Dissertations / Theses on the topic 'Plant water use'

Irrigation agriculture is the largest use of water (~80%) in the United States ('Irrigation and Water Use', 2016) A combination of irrigation and precipitation infiltrates through the Earth's subsurface and represents the primary inputs to an agricultural field's groundwater system. This water propagates down from the surface, with some of it recharging the underlying groundwater storage as return flow. The difference between the amount of irrigation water applied and the return flow to the aquifer, represents the consumptive use of the system. The alterations in the quality and distribution of water from groundwater pumping and irrigation places greater emphasis on the need to understand the connection between agricultural consumption and subsurface groundwater flux. Temperature fluctuations in the Earth's shallow subsurface are mainly governed by spatial and temporal variations in temperature at the ground surface (Hatch et al., 2006). These temperature signals at depth are primarily controlled by advection, dispersion, and thermal conduction. It has been shown for streambeds that when temperature propagates through the subsurface, it is a nonlinear function of fluid velocity, the frequency of the surface temperature variations, and the sediment and fluid thermal properties (Stallman, 1965). This information has been useful for understanding fluxes for saturated conditions such as in stream systems, but has not yet been applied to understand consumptive use in unsaturated conditions such as in agricultural systems. Temperature propagation in unsaturated conditions is different than saturated conditions due to changes in soil and thermal properties. Previous models have had difficulty estimating groundwater fluxes for some unsaturated conditions. This study experiments with the possibility of using a combination of MATLAB and HYDRUS 1D to infer unsaturated groundwater fluxes, saturated hydraulic conductivity, and saturated water content. One application of this type of flux estimation could be the inference of root water uptake and the consumptive use of an agricultural system. The method is designed to calculate root water uptake under steady-state conditions; and therefore might have limitations for quantifying consumptive use in field applications.It is beneficial to research the consumptive use in agricultural systems in order to gain understanding of the effects of irrigation on the total flux in groundwater storage. Other applications of consumptive use include: site specific farm efficiency and crop use parameters, nonpoint source pollution to estimate nutrient fluxes, irrigation efficiency, soil salinization, waste isolation, and slope stability.

Water is lost from higher plants via transpiration through stomatal pores the aperture of which is regulated by pairs of guard cells. Genetic engineering of the guard cell abscisic acid (ABA) signalling network that induces stomatal closure under drought stress is a key target for improving crop water use efficiency. In this study experiments were designed to investigate whether the biochemical mechanisms associated with the N-end rule pathway of targeted proteolysis could be involved in the regulation of stomatal apertures. The results indicate that the gene encoding the plant N-recognin, PRT6 (PROTEOLYSIS6), and the N-end rule pathway, are important in regulating stomatal ABA-responses in addition to their previously described roles in germination and hypoxia. Direct measurements of stomatal apertures showed that plants lacking PRT6 exhibit hypersensitive stomatal closure in response to ABA, and IR thermal imaging revealed reduced evapotranspiration under drought-stress. Together with a reduction in stomatal density, these properties result in drought tolerant plants. Plants lacking PRT6 are able to synthesis NO but their stomata do not close in response to NO suggesting that PRT6 is required for stomatal aperture responses to NO. Double mutant studies suggested that PRT6 (and by implication the N-end rule pathway) genetically interacts with known guard cell ABA signalling components OST1 and ABI1, and that it may act either downstream in the same signalling pathway or in an independent pathway. Several other enzymatic components of the plant N-end rule pathway were also shown to be involved in controlling stomatal ABA sensitivity including arginyl transferase and methionine amino peptidase activities. These results indicate that at least one of the N-end rule protein substrates which mediates ABA sensitivity has a methionine-cysteine motif at its N-terminus. A separate set of experiments were designed to investigate whether stomatal ABA-signalling pathways could have been conserved throughout land plant evolution. Cross-genetic complementation experiments were carried out to determine whether Physcomitrella stomatal apertures are able to respond to ABA and CO2 using a similar signalling pathway to that of flowering plants. The results demonstrated involvement of OST1 and ABI1 orthologues indicating that the stomata of the moss respond to ABA and CO2 using a signalling pathway that appears to be directly comparable to that of the model flowering plant Arabidopsis thaliana.

Almond water use was investigated at the leaf, plant and canopy level under a range of irrigation conditions in commercial orchards in California. Understanding plant response to water stress, specifically the behavior of plant transpiration and water use during periods of water stress, has important implications for irrigation scheduling in agriculture but also for water resources management and policy making.

Leaf gas exchange measurements of stomatal conductance and photosynthetic rate were performed at midday on shaded and on sunlit leaves, with midday stem water potential used to assess plant water stress. An essentially linear decline in both photosynthetic rate (from 25 to 5 μmol m^-2 s^-1) and stomatal conductance (from 400 to 50 mmol m ^-2 s^-1) as stem water potential declined over the range of -0.5 to -3 MPa was observed in sunlit leaves. These data indicated a strong sensitivity of leaf-level physiological processes to water stress. However, evapotranspiration at the canopy level, measured using Eddy Covariance, did not show a reduction relative to atmospheric demand during periods of water stress. The apparent disconnect observed between leaf conductance, responsive to water stress and canopy evapotranspiration, insensitive to water stress, is the central problem investigated in this study.

When the transpiration data was analyzed in the framework of a "Big Leaf" model, decoupled conditions (i.e. a limited stomatal control of transpiration) were shown to prevail at the experimental site, contrary to previous findings reported in the literature for tall crops such as almond orchards. Low coupling implies only a moderate sensitivity of transpiration to stomatal closure. Measured coupling increased substantially with wind speed but showed a wide range of values at the low wind speeds (<1m s^-1) that were observed at the site. At any wind speed however, higher canopy resistance resulted in higher coupling. The high leaf area index observed in the orchard may have been responsible for causing decoupled conditions, because when leaf area decreased as a result of harvesting operations, canopy transpiration appeared to become more sensitive to water stress.

Cumulative daily sap velocity was used as an estimate of plant transpiration. At the plant level, contrasting behaviors were observed in plant transpiration in the presence of water stress, depending on the duration and intensity of the stress. During long soil dry-down periods encompassing several weeks, plant transpiration relative to the evaporative demand of the atmosphere showed a statistically significant decline associated with a decrease in stem water potential and in stomatal closure. However, when the cycle of water stress was short (days), reductions in stem water potential seemed to be associated with an increase in cumulative sapflow velocity. The analysis of these results led to the development of a simple model that describes the theoretical interactions between three dependent variables, namely stem water potential, stomatal conductance and transpiration. The model output suggested that in wet soil, an increase in transpiration may be caused by increasing evaporative demand even if stem water potential and stomatal conductance decrease.

The Bromeliaceae is one of the largest and most ecologically diverse angiosperm families in the Neotropics. In recent years, this family has begun to emerge as a model system for the study of plant evolutionary ecology and physiology, and major advances have been made in understanding the factors involved in episodes of rapid diversification and adaptive radiation in specific bromeliad lineages. However, despite a long tradition of ecophysiological research on the Bromeliaceae, an integrative, evolutionarily-contextualised synthesis of the links between anatomical) physiological, and ecological aspects of bromeliad biology has hitherto been lacking. The overarching aim of this research project was therefore to use new quantitative data representing a wide range of bromeliad taxonomic and functional groups to elucidate how variation in leaf traits connected by structure-function relationships influences ecological differentiation among bromeliad taxa. Special emphasis was placed on hydraulic and water relations traits because of fast-paced contemporary developments in these fields. The methodologies employed included an assessment of the diversity of bromeliad hydrological habitat occupancy, quantification of key anatomical and physiological traits and their correlations, investigation of the links between vascular and extra-xylary anatomy and hydraulic efficiency and vulnerability, quantification of stomatal sensitivity to leaf-air vapour pressure deficit and stomatal kinetics, and a case study of trait-mediated niche segregation among congeneric epiphytic bromeliad species on the Caribbean island of Trinidad. The results highlight how divergences in a range of continuous and categorical anatomical traits underpin differences in physiological capacities and sensitivities, which in turn determine environmental relations and ecological distinctiveness. This research project therefore provides critical insights into the mechanistic basis of evolutionary diversification in a highly ecologically important family. It also represents the most comprehensive analysis of the significance of trait variation for ecological differentiation across any major radiation of herbaceous angiosperms.

Doctor of Philosophy
Department of Horticulture, Forestry, and Recreation Resources
Dale Bremer
Greg Davis
In 2005, turfgrass was estimated to cover approximately 20 million ha of urbanized land. That area is increasing with rapid urbanization, stressing the importance of water conservation in the lawn and landscape industry. Turfgrasses have been identified for replacement by presumably more water-efficient ornamental plant species to conserve water. However, research comparing drought resistance and evapotranspiration (ET) of turfgrasses with ornamental landscape plants is limited. Two studies were conducted to evaluate water use and performance under drought stress of several ornamental and turfgrass species. An online course was developed to educate students about critical water issues related to irrigation in urbanizing watersheds. In a field study, ET was measured using lysimeters and plant water status was evaluated under deficit irrigation (100%, 60%, and 20% ET) in Festuca arundinacea Schreb., Buchloe dactyloides (Nutt.) Engelm. ‘Sharps Improved’, and Ajuga reptans L. ‘Bronze Beauty’. Evapotranspiration was similar between A. reptans and F. arundinacea, and was 32 and 35% greater than ET of B. dactyloides. In a greenhouse study, the performance of one turfgrass (Poa pratensis L. ‘Apollo’) and eight landscape species (Achillea millifolium L., Ajuga reptans L. ‘Bronze Beauty’, Liriope muscari Decne., Pachysandra terminalis Siebold and Zucc., Sedum album L., Thymus serpyllum L., Vinca major L., and Vinca minor L.) was evaluated during a severe dry down and subsequent recovery. S. album, L. muscari, and P. terminalis performed the best, requiring 86 to 254 d to decline to a quality rating of one (1-9 scale: 1=dead/dormant, 9=best quality). The remaining species required 52 to 63 d. The only species to recover were P. pratensis [46% pot cover (PC) after 60 days], S. album (38% PC), and V. major (35% PC). A survey was developed to measure student learning as it relates to the level of sense and meaning present in the content of a new online course entitled “Water Issues in the Lawn and Landscape.” Survey results were compared with student learning as measured through a post-test. Post-test scores declined as the difference between sense and meaning increased (r =-0.82; P=0.03), indicating student learning is higher when both sense and meaning are present.

Doctor of Philosophy
Department of Horticulture, Forestry, and Recreation Resources
Dale J. Bremer
Jack D. Fry
Researchers and practitioners can use numerous techniques to measure or estimate evapotranspiration (ET) from turfgrass but little is known about how they compare to ET using standard lysimeters. An investigation was conducted to compare measurements of ET from lysimeters (LYS[subscript]E[subscript]T) with ET estimates from the FAO56 Penman-Monteith (PM[subscript]E[subscript]T) and Priestley-Taylor (PT[subscript]E[subscript]T) empirical models, atmometers (AT[subscript]E[subscript]T), eddy covariance (EC[subscript]E[subscript]T), and a canopy stomatal conductance model that estimates transpiration (COND[subscript]T). Methods were compared at the same site during the 2010, 2011, and 2012 growing seasons. Overall, PT[subscript]E[subscript]T and EC[subscript]E[subscript]T were not different from LYS[subscript]E[subscript]T, whereas PM[subscript]E[subscript]T, AT[subscript]E[subscript]T, and COND[subscript]T, increasingly underestimated LYS[subscript]E[subscript]T. Differences exist among ET measurement techniques and one should employ the technique that best fits their situation. An atmometer is an inexpensive tool that can be used to measure turfgrass ET within microclimates, such as those typically found in an urban home lawn. An investigation was conducted to compare AT[subscript]E[subscript]T estimates with PM[subscript]E[subscript]T estimates within a number of lawn microclimates. Home lawns in Manhattan and Wichita, KS, were selected for study during the growing seasons of 2010 and 2011. Open sward AT[subscript]E[subscript]T was 4.73 mm d[superscript]-[superscript]1, whereas PM[subscript]E[subscript]T was 5.48 mm d[superscript]-[superscript]1. Within microclimates, AT[subscript]E[subscript]T was 3.94 mm d[superscript]-[superscript]1 and PM[subscript]E[subscript]T 3.23 mm d[superscript]-[superscript]1. Atmometers can provide practitioners with reliable estimates of PM[subscript]E[subscript]T within microclimates. Zoysiagrass (Zoysia spp.) is a common turfgrass used on home lawns and golf courses. However, poor shade tolerance and cold hardiness have limited its use in the transition zone. A study was conducted to determine changes and differences in growth and physiology among selected Zoysia over a three-year period (2010-2012) in the transition zone. The genotypes were 'Emerald' [Z. japonica × Z. pacifica], 'Zorro' [Z. matrella], 'Meyer' and Chinese Common [Z. japonica], and experimental progeny Exp1 [Z. matrella × Z. japonica], and Exp2 and Exp3 [(Z. japonica × Z. pacifica) × Z. japonica]. 'Zorro' and 'Emerald' experienced winter injury. 'Meyer', Chinese Common, and Exp1 showed poor performance over the three-years. The Exp2 and Exp3 progeny, maintained high percent cover, visual quality, and tiller density, and may provide practitioners more shade-tolerant cultivar choices in the transition zone.

Winter wheat (Triticum aestivum L.) is the most extensive arable crop in the UK grown on about 2M ha p.a. There is a need to identify traits to ameliorate yield losses to drought which are on average about 15% per year. These losses will be exacerbated with predicted climate change. The overall objectives of the present study were to investigate the physiological and genetic bases of water-use efficiency (ratio of above-ground dry matter production to evapotranspiration; WUE) in winter wheat grown in UK conditions and to quantify relationships between WUE and yield performance under drought. The present study used a doubled haploid (DH) population of 33 lines derived from a cross between Beaver and Soissons, known from previous work to contrast for WUE. Two glasshouse experiments (2002/3 and 2003/4) and two field experiments (one at ADAS Gleadthorpe, Nottinghamshire in 2002/3 and the other at Sutton Bonington, University of Nottingham in 2004/5) were conducted. In the glasshouse experiments, two irrigation treatments (with and without irrigation) were applied to four genotypes (two parents and two DH lines), and in the field two irrigation treatments (rainfed and fully irrigated) were applied to the two parents and the 33 DH lines. A range of physiological traits was measured, including developmental stages, carbon isotope discrimination (Δ13C), leaf gas-exchange variables, green areas and biomass at sequential samplings, and these traits were related to grain yield. Transpiration efficiency (ratio of above-ground dry matter production to transpiration; TE) was assessed using the established inverse relationship between TE and Δ13c. In the glasshouse, WUE measured as the regression slope of dry matter on water use, did not differ amongst genotypes in 2003, but did in 2004. Soissons showed higher WUE than other genotypes under irrigation, and also higher WUE than Beaver under drought. For measurements of TE according to Δ13. Soissons and line 134G showed lower Δ13C values (higher TE) than line 134E and Beaver (P<0.05) in 2004 under both irrigation and drought. Soissons and line 134G showed consistently higher TE on account of lower stomatal conductance (gs ) and sub-stomatal C02 concentration (C) values. The early developing Soissons and line 134G exhibited greater flag-leaf green area persistence under drought than the late developing Beaver. Beaver tended to use more water than Soissons under both irrigation and drought, but reductions in water use under drought were similar amongst genotypes. Lower seasonal water use for Soissons than Beaver was associated with a smaller root system. There was a tendency for dry matter of Beaver to be more depressed under drought than Soissons in both the years. Overall, it was not possible to detect significant differences in biomass responses to drought amongst the genotypes, but there were consistent genetic differences in WUE and TE observed under both irrigated and droughted conditions. In the field experiments, the onset of drought coincided broadly with anthesis. The average grain yield losses under drought were 0.5 t ha-1 in 2003 and L6 t ha-1 in 2005. Averaging across site/seasons, Δ13C correlated positively with grain yield amongst the 35 genotypes under irrigation (r--0.35; P<0.05) and under drought (r--0.54; P<0.01), indicating a negative trade off between TE and yield. A 13C decreased under drought and a higher TE was associated with a reduction in average flag-leaf gs, measured from flag leaf emergence to anthesis + 4weeks. Stomatal conductance was measured for eight of the 33 DH lines including the parents, and there was a trend for lower Δ13C (higher TE) to be associated with lower gs, The genetic differences in gs, were generally associated with corresponding decreases in Ci and net photosynthetic rate (A). Therefore results suggested that the negative relationship between TE, as indicated by Δ13C and yield was associated with corresponding reductions in seasonal water use. There was a nonsignificant irrigation x genotype interaction at Gleadthorpe in 2003 and Sutton Bonington in 2005 for Δ13C indicating that this trait was of high heritability. There was an irrigation x genotype interaction for grain yield (P<0.05). A small number of genotypes showed higher yield associated with low Δ13C and these outlier lines could potentially be identified for breaking the negative linkage between yield and delta. In summary, WUE was negatively correlated with yield under drought in this population; and season-long water use appeared to be the most important component affecting yield levels under drought. It is suggested that selecting genotypes indirectly for high Δ13C (low WUE) may be a strategy to improve grain yield under drought. In the quantitative genetic analysis, the putative QTLs identified for target physiological traits were generally different at Gleadthorpe in 2003 and Sutton Bonington in 2005. The most confident putative QTLs for Δ13C were mapped on chromosomes 3B (LOD=2.32) and 2D (LOD=1.43). The identification of QTLs as potential candidate genes on these chromosomes may be associated directly with WUE in the Beaver x Soissons DH mapping population. The Δ13C QTL on chromosome 3B was detected commonly in both the irrigation environments and the direction of allelic effects was consistent with the parental differences in Δ13C. This QTL may therefore represent a novel gene for optimising WUE. It is suggested that breeders could optimise TE by selection according to a marker for this gene involving further fine-mapping to identify a marker tightly linked to the gene. Such a marker would also provide a target for gene discovery in future work. The results suggest that water use is the most important component of Passioura's yield model for yield improvement under UK conditions. Nevertheless, WUE and harvest index and their responses under drought will also likely play a role in yield improvement through breeding in the UK targeted at drought-prone environments in future years.

Presumably, from a physiological standpoint, early season water stress should be avoided to ensure early fruit initiation, good fruit retention, and optimum yield potential of cotton (Gossypium spp.). This study was conducted to determine the optimum timing of the initial post plant irrigation and the long term effect of postponement on subsequent plant growth patterns, fruit retention, and yield. A short - season Upland variety, (G. hirsutum L.), DPL 20, was planted on 19 April in Marana, AZ, elevation 1970 ft. , on a Pima clay loam (Typic Torrifluvent) soil. Plots (experimental units) consisted of eight 40 in. rows and extended the full length of the irrigation run (600 ft.). Experimental design was a randomized complete block with four replications. Initial post - plant irrigations, designated T1 , 72, and T3, were applied when the midday leaf water potential (ψ) of the uppermost, fully- developed leaf reached -15, -19, and -23 bars, respectively. All treatments received the same irrigation regime following the initial post plant irrigation. Basic plant measurements were taken weekly from each experimental unit. These included plant height, number of mainstem nodes, location of first fruiting branch, fruit retention, number of nodes above the uppermost white bloom, bloom count within a 166 ft² area, and percent canopy cover. Soil -water data at seven 25 cm depth increments was collected from a total of 36 access tubes located within the field study, with three tubes per plot. Lint yields (lb. lint /acre) were 1112, 1095, and 977 for T1 , 72, and T3, respectively. Yields were significantly lower when the initial post plant irrigation was applied after ψ, dropped below -19 bars, confirming the results of a previous study conducted in 1992. Throughout the growing season, height - node ratios (HNR) of T1 and 72 plants were at or above the upper threshold established for DPL 20, while T3 HNR remained close to the expected baseline. Fruit retention was low for all three treatments due to season -long insect pressure from lygus bug. The low fruit retention data reflects the effects of high HNR. Future work will include efforts to separate changes in ψ due to day-to-day climatic variations from those caused by soil -water depletion. A second objective will be to incorporate the data obtained from the neutron moisture meter probe into the study results in an effort to better describe the complete soil-plant-atmosphere continuum as affected by the various treatment regimes employed in this study.

Thyme is one of the best known genera because of its diverse medicinal and culinary uses. To understand plant response to drought, a range of genotypes of thyme was examined including Thymus vulgaris, T. serpyllum, T. daenensis, T. kotchyanous, T. capitata and T. zygis. Drought stress was imposed on 30 day old plants and some morpho-physiological traits were measured. Together these traits indicated that T. serpyllum was the most tolerant and T. vulgaris the most susceptible populations. Metabolite profiling using direct-infusion FT-ICR mass spectrometry identified differences in both polar and non-polar fractions. These results suggested that mechanisms adapting thyme to drought may include osmotic adjustment, ROS scavenging, cellular components protection, membrane lipid changes and hormone activity in which the key metabolites were proline, betaine, mannitol, sorbitol, ascorbate, JA, SA, ABA precursor, unsaturated fatty acids and tocopherol. Profiling of volatiles using GC/MS, showed an increasing-decreasing trend at major terpenes apart from thymol, alpha-cubebene and germacrene in sensitive plants. These results suggests that tolerant and susceptible populations of thyme employing different strategies in response to drought. In conclusion, the combination of metabolite profiling and physiological parameters contributed to a greater understanding of the mechanisms of thyme plant response at metabolomics level.

A general paradigm in semi-arid and arid systems is that woody plants with dimorphic root systems will exhibit preferential use of deeper soil water because it represents a more stable source of water than short duration pulses of shallow soil moisture derived from summer rainfall. However, whether this holds across all woody species and whether use of deeper soil water interacts with use of shallow soil water is not determined for many species in different ecosystems. Understanding the amount of water plants derive from groundwater and shallow soil water is critically important to accurate calculations of local and regional water balance. The focus of this research was to determine if dominant woody species in semi-arid riparian ecosystems used shallow soil water and how depth to groundwater and defoliation might affect root proliferation and water uptake. This research found that the functional grouping "phreatophytes" encompasses a variety of responses to environmental variation. Stable isotopic analyses determined that Prosopis velutina Woot. (Velvet mesquite) and Populus fremontii Wats. (Fremont cottonwood) used shallow soil water derived from summer rainfall, and the proportion of shallow soil water was higher at sites with greater depth to groundwater. In contrast Salix gooddingii Ball (Goodding willow) did not use shallow soil water at any location regardless of depth to groundwater. Field experiments using defoliation treatments, to limit carbon assimilation and reduce plant photosynthate pools, confirmed that Prosopis velutina exhibited flexible response in water uptake patterns in response to defoliation. Defoliation, which presumably reduced available photosynthate, increased the reliance of this species on shallow soil water; contrary to predictions that woody species should maintain extensive deep root systems to buffer themselves from seasonal drought. Greenhouse experiments with Populus fremontii and Prosopis velutina also indicated changes in belowground biomass of fine roots, which were associated with changes in water-source use for Populus fremontii, but not for Prosopis velutina. These results imply that in terms of predicting plant response to changes in future climates, or modeling fluxes of water from the soil to the atmosphere that are largely controlled by plant transpiration, intra- and interspecific variability will need to be considered.

Silicon is not considered an essential nutrient, but it is typically abundant in soils and can be taken up in large amounts by plants. Silicon is known to have beneficial effects when added to rice and several other plants. These effects include disease and insect resistance, structural fortification, and regulation of the uptake of other ions. In this study, the effect of silicic acid fertilization on the growth and drought tolerance of four crop plants (corn, wheat, soybean, and rice) was analyzed. Plants were studied using three cultivation techniques: 1) hydroponic solution and subjected to salt stress, 2) low-silicon soil-less medium (peat) and subjected to gradual drought stress, and 3) low-silicon soil-less medium (peat) and subjected to acute drought stress. Silicon was added both as reagent-grade Na2SiO3 and as a siliceous liming agent (PlantTuff). Both forms of Si generally improved drought and salt stress tolerance, but the effects were inconsistent. Silicon increased corn dry mass by up to 18% and the effect was statistically significant (p<0.05) in two out of three techniques. Silicon increased water use efficiency in corn by up to 36% and the effect was statistically significant (p<0.05) in one out of two techniques. In the acute drought stress technique, silicon increased wheat dry mass by 17% and the effect was statistically significant (p<0.05). Silicon increased soybean and rice dry mass by 20 to 30%, but the effect was not statistically significant. Silicon in oldest corn leaves increased from 0.4% to 3% as Si increased from less than 0.01 to 0.8 mM in the hydroponic solution. There was a statistically significant effect of silicon supply on the concentration of some other nutrients, but the effect was often not great enough to be considered biologically important. Rice accumulated the greatest concentration of foliar silicon, corn and wheat were intermediate, and soybean accumulated the least. Collectively, these results indicate an effect of silicon in drought and salinity stress tolerance, but additional studies on the rate and onset of drought are needed to determine interacting factors and better understand the inconsistent results.

The 9-cis-epoxycarotenoid-dioxygenase (NCED) is a key regulatory enzyme in ABA biosynthesis in plants and its overexpression increases ABA levels that can increase water use efficiency (WUE). The use of the „super promoter‟ (sp) to drive an LeNCED1 transgene in tomato greatly improved WUE without affecting long-term plant growth but caused delayed seed germination and reduced rates of seedling establishment. The first aim of the present study was to generate useful, novel variation in NCED transgene expression by allowing an LeNCED1 transgene, driven by a histone H2A promoter (pH2A), to transpose to new positions in the genome. A stabilized activator element linked to a GUS marker gene (sAc) was used to allow transposition of an engineered dissociation element (Ds) containing the LeNCED1 transgene of format Ds1::pH2A::LeNCED1::Ds2 (T-DNA-Ds). In F1 (sAc × Ds) plants transposition was demonstrated by detection of empty donor site through PCR. The F2 generation was screened for stable integration of the Ds element and reduced gs. Three F3 families, namely 59F3, 102F3 and 116F3, were investigated: they showed multiple stable Ds transposition events, had low gs, and a range of growth rates. Genotype 102F5 had wild-type seed germination, higher bulk leaf ABA and xylem sap ABA and 60% higher gravimetric WUE (WUEp). However, 102F5 accumulated 32% less above ground dry weight than wild type under well-watered conditions 56 days after germination. The sAc and Ds approach allowed production of T-DNA-Ds and nptII kanamycin free 102F5 line which retained transposed Ds (Tr-Ds) elements. These progeny were cross pollinated with sAc to reactivate the transposition of the LeNCED1 transgene and should be an excellent material for generating further variation in ABA content. The second aim was to overcome the seed dormancy in high ABA, genotypes such as sp5 and sp12, by testing novel hydroxamic acid NCED inhibitors for their ability to stimulate germination and seedling establishment. Improvement in seed germination in sp12 was observed with two hydroxamic acid compounds, and an increase in seedling growth rate was also observed, although this was not statistically significant.

Lysimeter experimental studies were conducted in a greenhouse to investigate canola (Brassica Napus) plant water use, growth and yield parameters under three different water table depths of 30, 60, and 90 cm. Additionally, control experiments were conducted and only irrigation was applied to these lysimeters without water table limitation. Canola plant?s tolerance level to shallow groundwater was determined. Results showed that groundwater contributions to canola plant were 97, 71, and 68%, while the average grain yields of canola were 4.5, 5.3, and 6.3 gr for the treatments of 30, 60, and 90 cm water table depths, respectively. These results demonstrated that 90 cm water table depth is the optimum depth for canola plant to produce high yield with the least amount of water utilization.

Water use by mature and sprout (coppice) forms of Emory oak (Quercus emoryi) was estimated by the sap-flow method. Five standards and five coppice trees were sampled in an area that had been harvested for fuelwood and five mature trees were sampled in an uncut area. Differences were recognized between coppice and standards in the cut area and between coppice trees and mature trees from the uncut area. Regression equations were derived relating estimated annual water use to tree diameter, height, and crown measurements for both cut- and uncut-area trees. Seasonal water use by each tree form showed relationship to precipitation, but little relationship to temperature and relative humidity. Woodland density and tree size measurements facilitate extrapolation of water use from the 15 sampled trees to a per area basis. Water use was approximately 1900 cubic meters per hectare per year, based upon drc measurements, for the uncut area and 3168 cubic meters for the cut area. Estimated water use on a per unit area was approximately 1.67 times greater for the cut area than the uncut area.

[Truncated abstract] Understanding the ecohydrological dynamics of native vegetation can provide a benchmark for future efforts to restore landscape hydrology and allow predictions of potential landscape responses to climate uncertainty and associated changes in vegetation cover. The key drivers of evapotranspiration (Et) involved in maintaining a hydrological balance that minimises deep drainage in semi-arid ecosystems operate at a range of scales, and in this thesis I assessed the water relations of functionally and taxonomically diverse plant communities in south-western Australia from the leaf-level to ecosystem scale. For three key communities; heath shrubland, mallee (small multistemmed eucalypt) -heath, and open eucalypt woodland, populating a typical catenary sequence of soil types along a slope, I addressed the following questions: 1) What are the predominant water use strategies of wheatbelt native plant communities and what underlying trade-offs determine the distribution of plant water use strategies along the topographical gradient? 2) What are the roles of soil water and hydraulic limitation in controlling the spatial and temporal dynamics of transpiration in different functional types? 3) What is the magnitude and partitioning of total Et in the woodland community and what processes determine Et fluxes on a seasonal and annual basis? 4) What are the seasonal differences in Et among contrasting community-types and how do these patterns relate to canopy attributes and transpiration capacity along the topographical gradient? A key philosophical step in working with species-rich communities was to develop the concept of 'hydraulic functional types' (HFTs) to identify groupings of species using associations of physiological and morphological traits that define their hydrological functioning. .... However, as shallow soils dried during spring and summer, Et fluxes were significantly lower at the heath site (0.35 versus 0.66 mm day-1 for the woodland in February), demonstrating that the seasonality of Et fluxes differentiates communityscale contributions to regional water balance. Land-surface exchange of water over native vegetation is by no means uniform, but varies according to the spatial and temporal availability of water along topographical gradients. In general, shallow soils present fewer opportunities for water use partitioning and favour drought hardiness and a transpiration response that tracks recent rainfall patterns, whereas deeper soils promote greater differentiation in water use strategy and support canopies responsive to atmospheric demand. This thesis provides a unique description of ecosystem water balance in a global biodiversity hotspot by viewing complex vegetation mosaics in terms of their relevant hydrological units. This information is fundamental to sustainable agroforestry and revegetation efforts and our ability to gauge possible changes in vegetation structure and function under a changing climate.

The aim of the present thesis was to better understand the physiological role of the phytohormones jasmonates (JAs) and abscisic acid (ABA) during fruit ripening in prospect of a possible field application of JAs and ABA to improve fruit yield and quality. In particular, the effects of exogenous application of these substances at different fruit developmental stages and under different experimental conditions were evaluated. Some aspects of the water relations upon ABA treatment were also analysed. Three fruit species, peach (Prunus persica L. Batsch), golden (Actinidia chinensis) and green kiwifruit (Actinidia deliciosa), and several of their cvs, were used for the trials. Different experimental models were adopted: fruits in planta, detached fruit, detached branches with fruit, girdled branches and micropropagated plants. The work was structured into four sets of experiments as follows: (i) Pre-harvest methyl jasmonate (MJ) application was performed at S3/S4 transition under field conditions in Redhaven peach; ethylene production, ripening index, fruit quality and shelf-life were assessed showing that MJ-treated fruit were firmer and thus less ripe than controls as confirmed by the Index of Absorbance Difference (IAD), but exhibited a shorter shelf-life due to an increase in ethylene production. Moreover, the time course of the expression of ethylene-, auxin- and other ripening-related genes was determined. Ripening-related ACO1 and ACS1 transcript accumulation was inhibited though transiently by MJ, and gene expression of the ethylene receptor ETR2 and of the ethylene-related transcription factor ERF2 was also altered. The time course of the expression of several auxin-related genes was strongly affected by MJ suggesting an increase in auxin biosynthesis, altered auxin conjugation and release as well as perception and transport; the need for a correct ethylene/auxin balance during ripening was confirmed. (ii) Pre- and post-harvest ABA applications were carried out under field conditions in Flaminia and O’Henry peach and Stark Red Gold nectarine fruit; ethylene production, ripening index, fruit quality and shelf-life were assessed. Results show that pre-harvest ABA applications increase fruit size and skin color intensity. Also post-harvest ABA treatments alter ripening-related parameters; in particular, while ethylene production is impaired in ABA-treated fruit soluble solids concentration (SSC) is enhanced. Following field ABA applications stem water potential was modified since ABA-treated peach trees retain more water. (iii) Pre- and post-harvest ABA and PDJ treatments were carried out in both kiwifruit species under field conditions at different fruit developmental stages and in post-harvest. Ripening index, fruit quality, plant transpiration, photosynthesis and stomatal conductance were assessed. Pre-harvest treatments enhance SSC in the two cvs and flesh color development in golden kiwifruit. Post-harvest applications of either ABA or ABA plus PDJ lead to increased SSC. In addition, ABA reduces gas exchanges in A. deliciosa. (iv) Spray, drench and dipping ABA treatments were performed in micropropagated peach plants and in peach and nectarine detached branches; plant water use and transpiration, biomass production and fruit dehydration were determined. In both plants and branches ABA significantly reduces water use and fruit dehydration. No negative effects on biomass production were detected. The present information, mainly arising from plant growth regulator application in a field environment, where plants have to cope with multiple biotic and abiotic stresses, may implement the perspectives for the use of these substances in the control of fruit ripening.

Breeding plants that produce equivalent growth with reduced water input (improved water use efficiency (WUE)) is necessary for sustained future crop production. Water deficit induces redistribution and synthesis of the phytohormone abscisic acid (ABA) thereby restricting transpiration. ABA is synthesised via cleavage of oxygenated carotenoids (xanthophylls). This work involved two approaches and three key ratelimiting enzymes in the ABA biosynthesis pathway: 9-cis-epoxycarotenoid dioxygenase (NCED) β-carotene hydroxylase (BCH); and phytoene synthase (PSY). Increasing ABA production under optimal conditions by overexpressing SlNCED1 has been shown to reduce stomatal conductance and improve WUE. The first approach, part of a larger programme exploring the allelic variation of NCED1 in wild tomato species, describes the introgression of S. galapagense and S. neorickii NCED1 alleles into the cultivated tomato background S. lycopersicum cv. Ailsa Craig. Plants homozygous for SgNCED1, SnNCED1 and SlNCED1 alleles were compared for water use gravimetrically. It was concluded that SgNCED1 and SnNCED1 did not improve WUE. The second approach involved creating a transgenic rootstock that might provide sufficient extra root-sourced ABA under non-stressed conditions to improve WUE of a non-transgenic scion. Root tissues contain less carotenoids than photosynthetic tissues, which may limit increases in root ABA biosynthesis. To increase precursor flux through the pathway, transgenic lines simultaneously over-expressing SlPSY1, SlBCH2, and SlNCED1 were created by crossing two double transgenic lines. Isolated roots of a selected triple line (H-22-8-8) accumulated increased concentrations of carotenoids, ABA and ABA catabolites. Gravimetric water use trials revealed that WT/H-22-8-8 (scion/rootstock) grafts frequently showed improved; TEp, δ13C, exudate flow rate and ABA concentration. H-22-8-8 rootstock conferred a consistent, modest, daily water saving; significant in the absence of water stress. This indicates that the triple rootstock is capable of restricting stomatal opening and water use, without reducing biomass production.

Predicted climate change and increasing global populations suggest that water will become an increasingly scarce and valuable commodity. Breeding plants which produce equivalent yields with reduced water input is therefore vital to sustain and increase crop production in the future. The phytohormone, abscisic acid (ABA), is important in controlling plant responses to water stress. It may be possible to improve water use efficiency (WUE) by genetically modifying tomato and other species to maintain elevated levels of ABA under optimal (unstressed) conditions, thereby manipulating an intrinsic signalling mechanism which is known to mediate drought-induced alterations of stomatal behaviour. ABA is synthesised via the oxidative cleavage of C40 epoxycarotenoid precursors, a reaction catalysed by the key enzyme 9-cis-epoxycarotenoid dioxygenase (NCED). Pure breeding transgenic tomato lines constitutively over-expressing LeNCED1, known as sp5 and sp12, both have elevated ABA concentrations, which reduce stomatal conductance under optimal (unstressed) growth conditions, thus conserving soil water during periods when corresponding wild type (WT) control plants were inefficient in its use. Under well-watered conditions, whole plant transpiration efficiency (TEp) was significantly greater in both 'high ABA' lines (sp12 and sp5) than in WT plants. The over-expression of LeNCED1 was combined with over-expression of a gene (LeBCH2) encoding β-carotene hydroxylase (BCH), an enzyme acting earlier in the ABA biosynthetic pathway. These 'double transgene' lines (G28 and G29) consistently exhibited further improvements in ABA accumulation and TEp relative to corresponding 'single transgene' parental lines. Lines G28 and G29 respectively exhibited 37 and 54 % improvements in TEp relative to WT controls. When evaluated as a potential 'high ABA' rootstock, it was found that the 'double transgene' G29 line did not provide a sufficiently strong root-sourced signal to affect the stomatal behaviour of scions. To increase ABA biosynthesis in the roots further, a programme designed to combine the over-expression of three ABA biosynthetic genes (LeNCED1; LeBCH2; LePSY1) was initiated with the objective of obtaining a rootstock which produced sufficient ABA to affect stomatal behaviour when grafted onto WT scions. Unfortunately, there was insufficient time to complete this work by the end of the period reported in this thesis, although the programme is ongoing.

Non-native plants have invaded over 100 millions of acres of western arid land in the US and dramatically altered nutrient cycling rates. Changes in water cycling caused by invasive species are of particular interest because primary production in the Western US is typically limited by water availability and aquifer recharge reflects plant demand. Large-scale invasions can, therefore, be expected to cause large-scale changes in hydrological cycles, but until recently, there have been considerable limitations in the ability to measure the timing, location, and extent of water use. Here we injected a tracer, deuterated water (D2O), into five soil depths in two sampling periods (May and June) in two adjacent plant communities (native and non-native dominated). Plants were sampled at several distances from the tracer addition area to determine the horizontal and vertical extent of water use in native and non-native communities. The tracer injection was coupled with measurements of leaf level stomatal conductance, leaf area index, and volumetric soil water content to estimate plant transpiration. We found that both native and non-native plants transpired water from primarily the top 60 cm of the soil (>75%), with a particular emphasis (≥ 50%) on shallow soil water (<10 cm) while lateral roots did not exceed 50 cm for most species. Higher leaf area index resulted in significantly more water being transpired from the native community. Some sharp distinctions in timing and location of tracer uptake resulting from the differing phenologies of the dominant species in each community were observed and confirmed previous mechanisms thought to govern plant assemblages in these communities. In May, the non-native community dominated by annual grasses had higher tracer uptake at 10 cm than the native community but began using deep water (higher tracer uptake at 80 cm) as annual grasses senesced and tap-rooted fobs became dominant in June. The perennial native species, however, used the entire soil profile from the moment they became active until they senesced. Our approach shows promise for overcoming the lack of resolution associated with natural abundance isotopes and other enrichment approaches, and for providing detailed measurements of plant water-use space.

Avui dia a Espanya i en moltes regions del món s'enfronten al problema d'escassetat d'aigua i la disminució de les seves ofertes. D'altra banda, les projeccions dels models climàtics preveuen que l'escassetat d'aigua es convertirà en un dels problemes més importants en moltes zones del món. Aquest seriòs problema fa que sigui urgent millorar l’eficiència en l’ús d’aigua. Considerant aquest aspecte, l'objectiu general d'aquesta tesis ha estat millorar l'eficiència del reg mitjançant la utilització de nous protocols de reg en dos espècies d’arbres, cirerers (Prunus avium) i de platan d’ombra (Platanus x hispanica) per a produir fusta. Mitjançant l'aplicació de diferents estratègies de reg deficitari basades en mesures de la màxima contracció diària del diámetre del tronc (MCD) combinat amb la mesura de l'estat de l'aigua al sòl. Els assajos van ser realitzats els anys 2009 i 2010, en un hivernacle (primer capítol) i en camp obert (segon i tercer capítol) a les instal•lacions de l'IRTA a Torre Marimon. Els objectius del primer capítol van ser avaluar si la MCD és un bon indicador de l’estat hídric del cirerer a partir de les relacions amb altres indicadors fisiològics i ambientals; així mateix, es va obtenir un valor llindar d'aquesta variable per a utilitzar-lo en la programació de reg. Com s'esperava els arbres ben regats i els arbres estressats van presentar diferències significatives en les variables fisiològiques: conductància estomàtica foliar (gs), potencial hídric foliar de migdia (md) i el flux de saba diari (Qd); el potencial matricial del substrat (s) va disminuir a valors de - 33 kPa i el corresponent valor de MCD va ser aproximadament de 0.30 mm. Aquests valors són considerats llindars potencials per a planificar el reg cirerers joves. Aquests valors corresponen a un md de -2.3 MPa i una gs de 50 mmol m-2 s-1, els quals indiquen estrès sever. En la part B del primer capítol, l'objectiu era explorar si la sequera afecta el patró diàri i horari dels dos indicadors de l’estat hídric mesurats en continu com son la variació del diàmetre del tronc i el flux de saba. Els arbres estresats mostren un increment significatiu de la MCD i un decrement del flux de saba respecte als arbres ben regats. La MCD és més sensible que el SF diàri front l'estrès per sequera, principalment a causa de la variabilitat més gran del SF entre arbres. En els cicles diàris, la variació del diàmetre del tronc i el flux de saba estan relacionats per un bucle que es comporta diferent quan estàn ben regats o estan estressats. La variació del pendent de la relació entre les dues varibles entre les 8 i les 16 hores en situacions de sequera pot ser un indicador d’estrés. Els objectius del segon capítol van ser intentar millorar la gestió de reg en arbres, cirerer i plàtan d’ombra, mitjançant la implantació de nous protocols de reg deficitari regulat (RDImds) basat en el valor absolut de la MCD i el potencial matricial del sòl (s), també es va combinar amb l’us d’aigua regenerada en cirerers . Els resultats indiquen que no va haver cap efecte negatiu associat amb l’aplicació del tractament RDI en el creixement en diàmetre, alçada i cobertura verda relativa, ni en la conductància estomàtica en ambdues especies. La qualitat d’aigua de reg tampoc va afectar al creixement dels cirerers El tractament RDImds ha estalviat aigua sense cap efecte negatiu sobre el creixement de l'arbre, amb el mateix comportament quan s’ha regat amb aigua regenerada o aigua de pou. El protocol aplicat en 2009 podria ser recomanat per a cirerers joves, i el protocol aplicat en 2010 podria ser recomanat per als plàtans. En el tercer capítol, l'objectiu va ser evaluar un protocol de programació de reg basat en el s i la señal de laMCD (MCDRDI/MCD100%Etc) en cirerer i en plàtan d’ombra. Els resultats van indicar que tractaments de RDI basats en la señal de MCD no van tenir efecte negatiu en els indicadors de creixement dels arbres, ni en la MCD ni en la gs. El tractament RDIsenyal va estalviar el 20-30% de l'aigua en les dues espècies. Així com en el tractament RDImds, el protocol aplicat en 2009 es podria recomanar per als cirerers joves i el protocol utilitzat en 2010 es podria recomanar per a plàtans d’ombra. Aquest darrer tractament té la desventatja que es necessita un control, però a la vegada evita els problemes de la influència de les condicions ambientals en la MCD del tractament RDImds.
Hoy en día en España y en muchas regiones del mundo se enfrentan al problema de la escasez de agua y la disminución de sus suministros. Por otra parte, las proyecciones de los modelos climáticos preveen que la escasez de agua se convertirá en uno de los problemas más importantes en muchas zonas del mundo. La gravedad de problema hace que sea necesario mejorar la eficiencia del uso del agua. Considerando lo anterior, el objetivo general de esta tesis es mejorar la eficiencia del riego mediante la utilización de nuevos protocolos de gestión de riego en dos especies de árboles: cerezos (Prunus avium) y plátano de sombra (Platanus x hispanica) para producir madera. Mediante la aplicación de diferente estrategias de riego deficitario basadas en las medidas de la máxima contracción diaria del tronco (MCD) combinado con la medida del estado hídrico del suelo. Los ensayos se realizaron los años 2009 y 2010, en un invernadero (primer capítulo) y en campo (segundo y tercer capítulo) en las instalaciones del IRTA en Torre Marimon. Los objetivos del primer capítulo fueron evaluar si la MCD es un buen indicador del estado hídrico del cerezo a partir de las relaciones con otros indicadores fisiológicos y ambientales; asimismo, se obtuvo un valor umbral de esta variable para utilizarlo en la programación del riego Como se esperaba, los árboles bien regados y los estresados presentaron diferencias significativas en todas las variables fisiológicas: conductancia estomática (gs), potencial hídrico de la hoja al mediodía ( md) y flujo de savia diario (Qd); el potencial matricial del substrato ( s) disminuyó hasta -33, y el correspondiente valor de MCD fue aproximadamente 0.30 mm. Estos valores se consideran umbrales potenciales para la programación del riego de árboles jóvenes de cerezos. Estos valores se corresponden a un -2 -1 md de -2.3 MPa y una gs de 50mmol m s , los cuales indican estrés hídrico severo. En la parte B del primer capítulo B, el objetivo fue explorar si la sequía afecta al patrón diario y horario de dos indicadores continuos del estado hídrico como son la variación del diámetro del tronco y el flujo de savia. Los árboles estresados mostraron un incremento significativo de la MCD y un decremento del SF diario respecto a los bien regados. La MCD es más sensible a la sequía que el SF diario, debido principalmente a la mayor variabilidad entre árboles del segundo. En los ciclos diarios, la variación del diámetro del tronco y el flujo de savia horario están relacionados por un bucle que se comporta diferente cuando está regado o estresado. La variación de la pendiente de la relación entre las dos variables entre las 8 y las 16 horas en situaciones de sequía puede ser un indicador de estrés. Los objetivos del segundo capítulo fueron intentar mejorar la gestión del riego en árboles, cerezo y plátano de sombra mediante la implantación de nuevos protocolos de riego deficitario regulado basados en el valor absoluto de MCD (RDImds) y el potencial matricial de suelo ( s), también se combinó con el uso de agua regenerada en cerezos. Los resultados indicaron que no hubo ningún efecto negativo relacionado con los tratamientos de RDI en el crecimiento en diámetro y altura del tronco ni en la cobertura verde, ni en la conductancia estomática en ambas especies. El tratamiento RDImds ha ahorrado agua sin ningún efecto en el crecimiento de los árboles, con el mismo comportamiento cuando se ha regado con agua regenerada o agua de pozo. El protocolo aplicado en 2009 podría ser recomendado para cerezos jóvenes, y el protocolo aplicado en 2010 podría recomendarse para plátanos. En el tercer capítulo, el objetivo fue evaluar un protocolo de riego basado en el s y la señal de la MCD (MCDRDI/MCD100%Etc). Los resultados indicaron que tratamientos de RDIseñal no tuvieron ningún efecto negativo sobre los indicadores de crecimiento de los árboles ni en la MCD ni en la gs. El tratamiento RDIseñal ahorró un 20 - 30% de agua en las dos especies. Així com en el tractament RDImds, el protocolo aplicado en 2009 se podría recomendar para cerezos jóvenes y el protocolo utilizado en 2010 se podría recomendar para plátanos. Este último tratamiento tiene la desventaja que necesita un control, pero a su vez evita los problemas de la influencia de las condiciones ambientales en la MCD del tratamiento RDImds.
Nowadays in Spain and many regions in the world face the problem of water scarcity and decreasing of its supplies. Moreover, climatic model projected that water scarcity will become one of the most important problems in many areas of the world. This serious problem supposes an urgent need to improve water use efficiency. Considering this problems, the general objective of this work was to improve irrigation efficiency by using new irrigation management protocol in two different species cherry trees (Prunus avium) and plane trees (Platanus x hispanica) for timber production. By applying different deficit irrigation strategies, based on the dendrometry measurements and other plant based water status indicators combined by soil water status measurements. The essays were conducted in 2009 and 2010; the first parts were conducted in one greenhouse and the second and third parts in the open field at IRTA Torre Marimon facilities. The objectives of the first chapter were to evaluate if MDS is a reliable indicator of cherry plants water status through its relationship with physiological and environmental variables; moreover, to study from these relationships the possibility of derivation a threshold value of MDS that indicated maximum water stress level in order to use it for irrigation scheduling. As expected well irrigated and stressed trees presented significant differences in all physiological variables: stomatal conductance (gs), midday leaf water potential ( md) and daily sap flow (Qd); substrate water potential ( s) decreased till -33kPa and the corresponding MDS value about 0.30 mm. Those values could be considered potential threshold for irrigation scheduling of young cherry trees. Those values corresponded to md of -2.3 MPa and gs of 50 mmol m-2 s-1, indicative of severe water stress. In part B of this chapter, the objective was to explore if drought affected the daily and hourly pattern of two continuous indicators of water status, trunk diameter variation and sap flow. Stressed trees showed a significant MDS increase and SF decrease respect to irrigated trees. MDS was more sensitive than SF in front of drought stress, mainly due to the higher variability of SF from tree to tree. In the daily cycle values, trunk diameter variation and sap flow were related to each other via a loop that differs according to tree water status. The change in the slope of the relationship between the two varibles between 8 and 16 hours in drought conditions can be an indicator of stress. The aims of the second chapter were to improve managing irrigation in woody trees, cherry and plane tree, by applying a regulate deficit irrigation protocols based on the absolute value of MDS (RDImds) and soil water potential ( s), combined by reclaimed water in cherry trees. Results indicated no negative effect related with RDI treatments was noticed on cherry or plane trees growth as no any significant differences was noticed in trunk diameter growth rate (TGR), height and relative green cover (RGC)neither in stomatal conductance in both species. Water quality neither affected the grothw of cherry trees. The RDImds treatment combined with s saved water without any negative effect on tree growth, with the same behavior when irrigated with reclaimed water or well water. The protocol applied in 2009 would be recommended for young cherry trees, and the protocol applied in 2010 would be recommended for plane trees. In the third chapter, the objective was to evaluate an irrigation scheduling protocol based on the information obtained from soil status s and MDS signal (MDSRDI/MDS100%Etc) as precision tools for automated adjustment of deficit irrigation in cherry and plane tree. Results indicated that RDIsignal and s protocols had no negative effect on tree growth indicators TGR and RGC; also no clear differences were noticed between well irrigated and RDIsignal trees in MDS and gs. Our irrigation scheduling protocol based on MDSsignal and s can be considered a valid protocol for schedule irrigation in woody trees as it helped us to save about 20- 30% of water in both species without any negative effect on the trees growth. As well as in the treatment RDImds, the protocol applied in 2009 could recommend for young cherry and protocol used in 2010 could recommend bananas for shade. The latter treatment has disadvantage it takes control, yet avoid the problems of the influence of environmental conditions on MCD treatment RDImds.

Elevated phosphorus (P) loading of freshwater lakes and reservoirs often results in poor water quality and negative ecological effects. Critical source areas (CSA) of P in the watershed can be difficult to identify and control. A useful concept for identification of a CSA is the P risk index (P Index) that evaluates the P risk associated with distinct source and transport pathways. The objectives of this study were to create a GIS model that adapts the Minnesota (MN) P Index for use at the watershed scale in a mixed-use, mountain environment, and to evaluate its effectiveness relative to field-based assessment. A GIS-based model of the MN P Index, adapted for montane environments and relying primarily on publicly available geospatial data, was created and applied in the Wallsburg watershed, located in the mountains of Central Utah. One necessary data input, P found in plant residue of common Utah ecosystems, was found lacking after literature review. We experimentally determined a range of observed values from multiple ecosystems to adapt and validate the GIS model. The GIS P Index was evaluated against the results of 58 field scale applications of the MN P Index conducted throughout the watershed. The field-scale analysis resulted in about 14% of the sites sampled being identified as high or very high risk for P transport to surface water. Spatially, these high risk areas were determined to be a geographic cluster of fields near the lower middle agricultural section of the watershed. The GIS model visually and spatially identified the same cluster of fields as high risk areas. Various soil test P scenarios were explored and compared to the known 58 site values. Soil test phosphorus had little effect on the GIS model's ability to accurately predict P risk in this watershed suggesting that high volume soil sampling is not always necessary to identify CSAs of P. Variable hypothetical livestock density scenarios were also simulated. The GIS model proved sensitive to variable P inputs and highlighted the necessity of accurate applied P source data. On average the model under-predicted the known field-site values by a risk score of 1.3, which suggests reasonable success in P assessment based on the categorical risk scores of the MN P Index and some potential for improvement. The GIS model has great potential to give land managers the ability to quickly locate potential CSAs and prioritizing remediation efforts to sites with greatest risk.

Ground-based spectral imaging devices offer an important supplement to satellite imagery. Hand-held, ground-based sensors allow rapid, inexpensive measurements that are not affected by the earth’s atmosphere. They also provide a basis for high altitude spectral indices. We quantified the spectral reflectance characteristics of hard red spring wheat (Triticum aestivum cv. Westbred 936) in research plots subjected to either nitrogen or water stress in a two year study. Both types of stress reduced ground cover, which was evaluated by digital photography and compared with ten spectral reflectance indices. On plots with a similar soil background, simple indices such as the normalized difference vegetation index, ratio vegetation index, and difference vegetation index were equal to or superior to more complex vegetation indices for predicting ground cover. Yield was estimated by integrating the normalized difference vegetation index over the growing season. The coefficient of determination (r2) between integrated normalized difference vegetation index and final yield was 0.86. Unfortunately, none of these indices were able to differentiate between the intensity of green leaf color and ground cover fraction, and thus could not distinguish nitrogen from water stress. We developed a reflective index that can differentiate nitrogen and water stress over a wide range of ground cover. The index is based on the ratio of the green and red variants of the normalized difference vegetation index. The new index was able to distinguish nitrogen and water stress from satellite data using wavelengths less than 1000 nm. This index should be broadly applicable over a wide range of plant types and environments.

Sustainable vegetable production is one of the most active areas of vegetable research and of concern to all producers. Everyone, both producers and consumers, are concerned with sustainability. Brussels sprouts and sweet basil are high value commodities, but increasing global concerns about water availability, insect-pest problems, and costly fertilizer inputs severely impact the growth and production of these crops. Low tunnels covered with spun-bonded fabric can improve production of vegetables and herbs in Virginia and the U.S. This study investigated the performance of Brussels sprouts and basil grown under low tunnels (LTs), and their relationship with water use efficiency, nitrogen use efficiency, and the level of protection against insect injury. Low tunnels increased yield, number of sprouts, and water use efficiency of Brussels sprout production. In addition, LTs decreased irrigation requirements, irrigation events, leaf feeding injury, and insect populations in comparison to open field. Similarly, LTs increased summer production of sweet basil as measured by fresh weight and biomass. In addition, plant N uptake was greater under the LTs; however, the increase in nitrogen use efficiency was inconsistent.
Master of Science in Life Sciences
Brussels sprouts and sweet basil are economically important cash crops on the East Coast. Brussels sprouts is a Cole crop and an important source of dietary fiber, vitamins (A, C & K), calcium, iron, manganese and antioxidants. Similarly, sweet basil is a member of the mint family and important high-value herb in the U.S. and the world. It is mainly grown for culinary purposes as a dried and fresh spice in the U.S. However, demand for these commodities is increasing. Low tunnels (LTs) covered with spunbonded fabric can be a practical management tool to increase yield. Results from this study indicate that LTs increase yield of Brussels sprouts and basil, water use efficiency and total nitrogen uptake, while reducing insect pest infestation. Therefore, LTs can be a useful tool to improve sustainability of Brussels sprouts and basil production.

Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgico
A sensibilidade à salinidade varia com o estÃdio de desenvolvimento da cultura. O feijÃo-de-corda [Vigna unguiculata (L.) Walp.] constitui uma das principais culturas, em diversas regiÃes semi-Ãridas do mundo. Avaliou-se o efeito da irrigaÃÃo com Ãgua salina, aplicada em diferentes estÃdios de desenvolvimento de plantas de feijÃo-de-corda. O experimento foi conduzido no campo, e obedeceu ao delineamento em blocos ao acaso, com cinco tratamentos (T1, T2, T3, T4 e T5) e cinco repetiÃÃes. O feijÃo-de-corda foi cultivado no espaÃamento de 0,8 m entre linhas e 0,3 m entre plantas, com duas plantas por cova. Os tratamentos utilizados foram: T1 - plantas irrigadas com Ãgua do poÃo (CEa de 0,8 dS m-1) durante todo o ciclo; T2 - Ãgua salina com CEa de 5,0 dS m-1, com aplicaÃÃo iniciada apÃs a germinaÃÃo e permanecendo atà o final do ciclo; T3 - Ãgua salina com CEa de 5,0 dS m-1, da semeadura atà 22 dias apÃs o plantio (DAP), correspondendo Ãs fases de germinaÃÃo e crescimento inicial, e Ãgua do poÃo no restante do ciclo; T4 - Ãgua salina com CEa de 5,0 dS m-1, aplicada de 23 a 42 DAP (fase de intenso crescimento vegetativo atà a prÃ-floraÃÃo), e Ãgua do poÃo nas demais fases do ciclo; T5 - Ãgua do poÃo da semeadura atà 42 DAP e Ãgua salina (CEa de 5,0 dS m- 1) aplicada a partir dos 43 DAP (floraÃÃo e frutificaÃÃo). Foram avaliadas a cobertura vegetal do solo, crescimento vegetativo, fotossÃntese, transpiraÃÃo, condutÃncia estomÃtica, produtividade, partiÃÃo de matÃria seca, os teores, os totais extraÃdos e a distribuiÃÃo dos nutrientes na planta, a eficiÃncia nutricional, eficiÃncia no uso da Ãgua e o acÃmulo de sais no solo. A irrigaÃÃo com a combinaÃÃo de Ãgua do poÃo com Ãgua salina reduziu o acÃmulo de sais no solo, em relaÃÃo ao T2. O T2 reduziu as taxas de fotossÃntese e transpiraÃÃo, em relaÃÃo ao T1. O T3 provocou reduÃÃo das trocas gasosas somente na primeira mediÃÃo, enquanto, que similar aplicaÃÃo nos outros estÃdios (T4 e T5) nÃo provocou reduÃÃes significativas nas trocas gasosas das plantas. O T2 inibiu o crescimento vegetativo da planta, enquanto o T3 provocou retardo no desenvolvimento da planta. Os tratamentos T2 e T3 provocaram reduÃÃes significativas no nÃmero de vagens e na produÃÃo de sementes por planta, em relaÃÃo aos demais tratamentos. Por outro lado, os tratamentos T4 e T5 nÃo afetaram o crescimento e a produtividade da cultura, sendo que o T4 causou aceleraÃÃo no ciclo reprodutivo da cultura. Os minerais foram extraÃdos pelo feijÃo-de-corda na seguinte ordem decrescente: N > K > Cl > Ca > Na > P > Fe > Zn > Mn > Cu, no entanto, o T2 reduziu a extraÃÃo da maioria dos elementos analisados, com exceÃÃo do Na e Cl. Os minerais Na, Cl, K, Ca, Fe e Mn permaneceram preferencialmente nas partes vegetativas enquanto N e P foram exportados em maiores proporÃÃes pelos frutos. O T3 reduziu a eficiÃncia de utilizaÃÃo da maioria dos nutrientes. O T2 reduziu a eficiÃncia agronÃmica de utilizaÃÃo de N, P e K, entretanto nÃo afetou a eficiÃncia de utilizaÃÃo dos nutrientes extraÃdos pelas plantas.
The sensitivity of crops to salinity often changes from one growth stage to another. Cowpea [Vigna unguiculata (L.) Walp.] is an important crop specie cultivated in different semi-arid regions of the world. The objective of this work was to evaluate the effect of the irrigation with saline water, applied at different growth development stages of cowpea. The experiment was set up in the field, during the dry season. A completely randomized block design, with five treatments (T1, T2, T3, T4 and T5) and five repetitions, was adopted. The distance between lines and plants were 0.8 m and 0.3 m, respectively, with two plants per hole. The treatments studied were: T1 - Groundwater with electrical conductivity (ECw) of 0.8 dS m-1 during the whole crop cycle; T2 - Saline water (ECw = 5.0 dS m-1) during the whole crop cycle, starting after germination; T3 - Saline water (ECw = 5.0 dS m-1) from sowing until the 22th day after sowing (germination and initial growth) and groundwater in remaining stages of the crop cycle; T4 - Saline water (ECw = 5.0 dS m-1) from the 23th to the 42nd day after germination (intense growth and pre-flowering), and groundwater irrigation for the remaining growth stages. T5 - Groundwater from sowing to the 42nd day after sowing and saline water (ECw = 5.0 dS m-1) during flowering and pod-filling stages. Soil coverage, gas exchange, vegetative growth and crop yield were measured. The mineral concentration and quantity of nutrient removed from the soil, as well as the nutrient use efficiency and salt accumulation in soil were also determined. The irrigation with combination of groundwater and saline water reduced the salt accumulation in soil, in relation to continuous use of saline water. The continuous application of water with ECw of 5.0 dS m-1 (T2) reduced the rates of photosynthesis and transpiration, in relation to the well water (T1). Plants of the treatment 3 showed reduction in gas exchanges only in the first measurement, while the saline water application in other growth stages (T 4 and T5) did not provoke significant reductions in leaf in the gas exchanges of the plants. It was found that the continuous use of saline water inhibits plant growth, while the irrigation with saline water during germination and initial growth causes retardation in plant development. For treatments 2 and 3, reduction in the number of pods and in seed production was verified. Irrigation with saline water from the 23rd to the 42nd day (T4) and from the 43rd to the 63rd (T5) day after sowing did not affect reproductive and vegetative growth, but the saline water application in the pre-flowering (T4) caused anticipation of reproductive cycle. Cowpea plants removed the minerals analyzed in the following decreasing sequence: N > K > Cl > Ca > Na > P > Fe > Zn > Mn > Cu, but the continuous use of saline water (T2) reduced the total extracted for the most nutrients, except for Na e Cl. The minerals Na, Cl, K, Ca, Fe and Mn were distributed preferentially to vegetative plant parts, while the most of N and P were exported in the pods. The irrigation with saline water during germination and initial growth stage (T3) reduced the mineral use efficiency of most of analyzed nutrients. The continuous application of saline water (T2) reduced the agronomic efficiency of the fertilizer application (N, P and K), but it did not affect the nutrient use efficiency by the plants.

The recent growth of low-density urban developments in the Mediterranean coast has led to an increase in the number of private domestic gardens. This thesis examines the flora, features and management practices of 258 private gardens in the Alt Empordà region in Catalonia. We also calculated water requirements of gardens based on species composition and land cover, and determined whether they can be predicted from the socioeconomic, demographic and cultural characteristics of households. Of the 635 taxa identified, 68% were exotic. Moreover, 39 species have been considered potentially invasive in Spain, although only 25 were present within the limits of the adjacent Aiguamolls de l’Empordà Natural Park. The distribution of garden floras was significantly related to different socioeconomic and demographic gradients, such as the occupancy rate of the house, the origin of the residents, their income level and the percentage of unemployed members.
L’augment recent dels espais urbans de baixa densitat a la costa mediterrània ha comportat un increment del nombre de jardins privats. La present tesis estudia la flora, les característiques i les pràctiques de gestió de 258 jardins privats a la comarca de l’Alt Empordà. També es van calcular les necessitats hídriques dels jardins d’acord amb la seva composició i estructura vegetal, i es va determinar si es podien predir a partir de les característiques socioeconòmiques, demogràfiques i culturals de les llars. Dels 635 tàxons identificats, el 68% eren exòtics. A més, 39 espècies han estat considerades com a potencialment invasores a Espanya, encara que només 25 són presents dins dels límits del Parc Natural dels Aiguamolls de l’Empordà. La distribució de la flora del jardins es va relacionar significativament amb diferents gradients socioeconòmics i demogràfics, com ara la taxa d’ocupació, l’origen dels residents, el nivell d’ingressos o el percentatge de membres en atur.

Seawater usage in mineral processing has become a fairly topical issue in the 2010’s. The deficit of fresh water grows meanwhile the demand rises globally. Fresh water is a critical component, especially in many industrialized arid countries, where only available water source can be seawater or highly saline underground water. Currently many mining operations in water-scarce countries are utilizing desalinated seawater as process water, while few of them are using direct seawater. The aim of this Master’s thesis was to gain more understanding of the faced challenges in the Cu-Mo ores froth flotation in seawater. In the experimental work, synthetic seawater was utilized as process water in the laboratory rougher flotation tests. Tests were conducted in Outotec Research Center at mineral processing laboratory in Pori. The ore sample was porphyry Cu-Mo ore, which was delivered from north Chilean deposit Sierra Gorda. Two rougher flotation test series were conducted in synthetic seawater and tap water. In the first phase, the effect of using seawater as process water was investigated by using different type of collectors. The object of the second phase was to conduct flotation tests in synthetic seawater and tap water with varying dosages of lime, and observe the effects on pH, and on the recoveries of copper, molybdenum and sulfur. Recovery of copper maintained almost the same level in both mediums. However, lime consumption was observed to be increased significantly under flotation conditions in synthetic seawater. In addition, the floatability of molybdenum was affected negatively above the pH 9.5. The major cause for the buffering effect of seawater was studied to be due to the carbonate system, the boric acid-borate equilibrium and the concentration of Mg2+. Recovery reduction of molybdenum was suggested to occur due to the magnesium hydroxide complexes and magnesium hydroxide precipitates, which began to form in seawater in higher pH levels. These species have been claimed to affect negatively on the natural hydrophobicity of molybdenite. The experimental work showed that the conventional flotation of Cu-Mo ore conducted in seawater has serious conflicts, when pyrite is depressed with lime. Results indicate that rougher flotation of the Cu-Mo ore carried out in seawater gives sufficient recoveries for copper and molybdenum, at the expense of accepting large pyrite content in the froth. Hence, the difficulty of depressing pyrite will be problematic in the cleaning flotation, where higher pH levels are applied. Seems that the Cu-Mo ores flotation in seawater is in the need for a new kind of method that would depress pyrite without lime. A few solutions have already been developed, which can probably suppress the problem. A promising new method, named AMBS treatment, is not requiring lime to depress pyrite, and it has shown good metallurgical results for molybdenite, when flotation is conducted in seawater
Meriveden valjastaminen käyttöön rikastamojen prosessivetenä on noussut ajankohtaiseksi aiheeksi 2010-luvulla. Makeiden vesivarojen arvo nousee sitä mukaa, kun veden tarve kasvaa globaalisti. Makeasta vedestä on muodostunut kriittinen elementti erityisesti niille kuiville alueille sijoittuville teollistuneille maille, joille ainoa saatavilla oleva veden lähde on merivesi tai suolainen pohjavesi. Yhä useammat kuivissa maissa toimivat kaivosprojektit käyttävät toiminnoissaan suolapuhdistettua merivettä, kun osa näistä projekteista käyttää prosessivetenään raakaa merivettä. Tämän diplomityön tarkoituksena oli selvittää kupari-molybdeenimalmin vaahdottamisen haasteet, kun väliaineena käytetään merivettä. Työn kokeellisessa osuudessa keskeisessä osassa olivat laboratoriomittakaavan esivaahdotuskokeet, joissa prosessivetenä hyödynnettiin synteettistä merivettä. Kokeet toteutettiin Outotecin tutkimuskeskuksen rikastuslaboratoriossa Porissa. Malminäytteenä käytettiin porfyyri kupari-molybdeenimalmia, joka toimitettiin Sierra Gordan esiintymästä Chilestä. Kaksi esivaahdotus-koesarjaa suoritettiin synteettisessä merivedessä ja hanavedessä. Ensimmäisessä vaiheessa meriveden vaikutusta vaahdotukseen tutkittiin vertaamalla erityyppisten kokoojien tehokkuuksia samankaltaisissa vaahdotusolosuhteissa. Toisen vaiheen tarkoituksena oli suorittaa vaahdotuskokeita synteettisessä merivedessä ja hanavedessä lisäten vaihtelevia määriä kalkkia, jolloin tarkastelun kohteena olivat lietteen pH-luku, sekä vaikutukset kuparin, molybdeenin ja rikin saanteihin. Kuparin saanti pysyi likimäärin samalla tasolla kummassakin väliaineessa. Merivedessä kalkin tarpeen havaittiin lisääntyneen huomattavasti verrattuna hanaveteen, jonka lisäksi molybdeenin saanti laski merivedessä voimakkaasti, kun pH nostettiin yli 9.5. Kalkin kulutuksen lisääntyminen johtui meriveden puskurointikyvystä, jonka katsottiin aiheutuvan pääasiassa meriveden karbonaattisysteemistä, boorihappo-boraatti tasapainosta sekä Mg2+ ionin konsentraatiosta. Molybdeenin saannin laskun todettiin mahdollisesti johtuvan magnesiumista, joka muodostaa merivedessä kohonneessa pH:ssa kompleksisia magnesiumhydroksidi-ioneja sekä kiinteää magnesiumhydroksidia, joiden on todettu muokkaavan molybdeniitin luonnollista hydrofobisuutta. Kokeellisen osuuden tulokset viittaavat siihen, että pyriitin painaminen kalkilla on ristiriitaista, jos vaahdotus toteutetaan merivedellä. Kuparin ja molybdeenin saannit saadaan hyvälle tasolle esivaahdotuksessa sillä ehdolla, että suurempi pitoisuus pyriittiä hyväksytään rikasteeseen. Sen vuoksi pyriitin erottaminen kertausvaahdotuksessa voi olla ongelmallista, sillä kertauksessa sovelletaan esivaahdotusta korkeampaa pH:ta. Kupari-molybdeenimalmin vaahdotus merivedessä vaatii uudenlaisen menetelmän, jolla pyriittiä voidaan painaa tehokkaasti perinteistä menetelmää alhaisemmassa pH:ssa. Sopivia ratkaisuja on jo kehitetty, jotka voivat mahdollisesti poistaa ongelman. Niin kutsuttu AMBS käsittely vaikuttaa lupaavalta, sillä sen on todettu parantavan molybdeenin saantia merivedellä vaahdotettaessa ilman, että kalkkia tarvitaan lisätä pyriitin painamiseksi

Fruit growers in Utah and other areas across the Intermountain West are faced with growing production challenges stemming from declining soil quality and water resources. Population growth presents challenges in terms of the cost and availability of land, but also presents opportunities in the form of new marketing options such as organic fruit. Few certified organic fruit orchards are operating in Utah currently, which is attributed to a lack of locally tested and adapted organic management practices. An organic peach orchard trial evaluated the effectiveness of different organic management approaches to enhance soil quality and conserve water without compromise to fruit tree growth and fertility. Two tree-row treatments: ‘straw mulch' (Triticum aestivum L.) and ‘living mulch’ (Lobularia maritima (L.) Desv.) were tested in combination with two alleyway groundcovers: ‘grass’ (Festuca rubra L. with Lolium perenne L.) and a legume, ‘Birdsfoot trefoil’ (Lotus corniculatus L.). The novel systems were compared with industry standards, tillage and weed fabric tree-rows with grass alleyways. Trefoil alleyway biomass deposited into tree-rows contributed an estimated 6.24 kg biomass and 0.21 kg total N/tree annually. Trefoil treatments had higher levels of organic carbon (C) and nitrogen (N), inorganic N, microbial biomass and enzyme activities, suggesting trefoil alleyways enhanced soil nutrient cycling, as well as C and N reserves in comparison to grass and tillage treatments. A functional gene array analysis was conducted to describe the mechanisms, microbial functional composition and diversity underlying the observed soil processes, however few differences were detected in soil community structure between soils under different orchard floor management. Significantly lower leaf δ15N in trees grown with trefoil compared to grass, and an association between root biomass, diameter and trunk cross-sectional area (TCSA) suggests nitrogen sources derived from the trefoil groundcover contributed to improved fruit tree vigor. Few differences resulted among orchard treatments for water use (mm/week). Trends indicated slightly higher water use in trefoil over grass, but not enough to offset observed soil quality and tree growth benefits. These findings suggest, trefoil alleyways may provide ecological benefits such as improved soil quality and efficient nutrient cycling, without substantial increases in water use.

Worldwide, agriculture production continues to be constrained by a number of abiotic and biotic stresses. In areas with Mediterranean climate, drought events are expected to strengthen in terms of intensity, frequency and duration in the near future. Thus, in this area, soil water deficit is considered the main environmental factor influencing grapevine growth. At the same time, grapevines are highly subjected to different viruses from which Grapevine leafroll associated virus-3 (GLRaV-3) is one of the most widespread ones, provoking considerable economic losses in many vineyards worldwide. The identification of how different stress responses are integrated and how they affects plant growth and physiological traits, is therefore very important to ensure the continuity of vine growing. The first main objective of the present thesis was to study the sanitary status of Majorcan minority grapevines cultivars and to highlight the prevalence of GLRaV-3 in local cultivars. In this sense, the results showed that virus incidence is very high and can rise up (91.75 %) in the local grapevine cultivars conserved in the germplasm collection of the Balearic Islands. Remarkably, GLRaV-3 is the most prevalent virus in this collection (82 %). This situation urges a speedy implementation of the sanitation techniques in order to obtain virus-free certified plants. Hence, two sanitation techniques ―shoot tips culture and thermotherapy in combination with shoot tips culture‖ have been optimized for double and triple viruses‘ eradication from two local cultivars with high enological potential, Argamussa and Gorgollassa. The second main objective was to dissect the effects of virus infection, moderate water stress and its combination on main physiological processes in two local grapevine cultivars, Malvasia de Banyalbufar and Giró Ros. Each of the two studied stresses resulted in a negative effect on leaf gas-exchange parameters. Water stress in non-infected plants (WS-NI) significantly reduced plant growth and net CO2 assimilation (AN) but had only small effect on metabolic changes, indicating that AN changes were mainly constrained by diffusive parameters (stomatal (gs) and mesophyll (gm) conductance‘s). With regard to virus infection under well-watered conditions (WW-VI), the results also revealed that GLRaV-3 impaired AN through diffusional limitations rather than biochemical ones. In this case, stomatal conductance was mainly regulated by changes in hydraulic conductance at leaf level, namely leaf (Kleaf) and petiole (Kpetiole) hydraulic conductance, in which Kpetiole resulted to be the most relevant parameter to be checked when studding the effect of phloemetic viruses in plant hydraulics. Remarkably, the results of this thesis indicate that the combined stress resulted in a detrimental effect on plant growth and physiology; but any additive effect between WS and VI has been highlighted. Moreover, the combination of stresses triggers a specific response at the metabolic level, which was not quantitatively predicted by the sum of each individual stress. The observed changes in primary metabolites were closely associated with respiration metabolisms. Indeed, the specific adjustment of respiratory metabolism (i.e; cysteine, threonine, fumarate and erythronate 1,4-lactone) could potentially explain the maintenance of leaf carbon balance and growth in cultivars studies under combined stress conditions. In the present thesis, we move a step further, by revealing the importance of studding grapevine-virus infection-water stress interactions under field conditions, particularly, in white cultivars where viruses are asymptomatic and difficult to identify. Further research with differents virus concentration and high number of cultivars are needed to confirm if virus effect is concentration dependent and if there is a cultivar-susceptibility difference.
A escala mundial, la producción agrícola sigue estando limitada por una serie de estreses abióticos y bióticos. En las zonas de clima mediterráneo, es muy probable que, en un futuro próximo, la duración, la frecuencia y/o la intensidad de la sequía aumenten. De esta forma, en el mediterráneo, el déficit hídrico se considera el principal factor ambiental limitante del crecimiento de la vid. Al mismo tiempo, el cultivo de la vid está expuesto a diferentes enfermedades provocadas por virus, de los cuales el virus del enrollado 3 (GLRaV-3) es uno de los más extendidos, provocando importantes pérdidas económicas en muchos viñedos de grandes regiones vitícolas de todo el mundo. La identificación de cómo se integran las respuestas de diferentes estreses en la viña y también de cómo están afectando el crecimiento y la fisiología de las plantas es, por tanto, de gran interés para garantizar la continuidad del cultivo de la vid. El primer objetivo de esta tesis es estudiar el estado sanitario de las variedades minoritarios de la vid y destacar la incidencia del GLRaV-3 en las variedades locales de vid. Los resultados obtenidos han puesto de manifiesto que la incidencia de los virus es muy alta (91,75%) en las variedades locales de vid conservadas en la colección de germoplasma de las Islas Baleares. Sorprendentemente, en esta colección, GLRaV-3 es el virus que mostró una mayor incidencia (82%). En este sentido, instamos a la rápida aplicación de técnicas adecuadas de saneamiento para obtener plantas certificadas libres de virus. Por ello, se han optimizado dos técnicas de saneamiento " cultivo in vitro de ápices caulinares y la combinación de termoterapia y cultivo in vitro de ápices caulinares‖ para la erradicación de las infecciones víricas dobles y triples de dos cultivares locales de gran potencial enológico, Argamussa y Gorgollassa. El segundo objetivo principal de esta tesis es explorar los efectos del estrés hídrico, la infección vírica y la combinación de ambos sobre los principales procesos fisiológicos de dos variedades locales de vid, Malvasia de Banyalbufar y Giró Ros. Cada uno de los dos estreses estudiados resultó en un efecto negativo sobre los parámetros de intercambio gaseoso foliar. El estrés hídrico in plantas sanas (WS-NI) redujo significativamente el crecimiento de las plantas y la asimilación neta de CO2 (AN), pero solo demostró tener un efecto reducido sobre los niveles metabólicos, indicando en este caso, que los cambios de AN durante el WS se ven limitados por factores difusivos (la conductancia estomática (gs) y del mesofilo (gm)). Respecto a las plants infectadas en condiciones de riego (WW-VI) las correlaciones obtenidas entre los parámetros fisiológicos (AN, gs y gm), la concentración de virus y los metabolitos sugiere firmemente que el GLRaV-3 afecta a la AN mediante limitaciones difusivas más que bioquímicas. En este caso, la conductancia estomática fue regulada principalmente por la conductancia hidráulica a nivel foliar, concretamente conductancia hidráulica de hoja (Kleaf) y pecíolo (Kpetiole). En este trabajo, Kpetiole resultó ser el parámetro más relevante para estudiar el efecto de los virus sistémicos de tipo floemático sobre la hidráulica de la planta. Notablemente, los resultados de esta tesis indican que el estrés combinado tuvo un efecto negativo sobre el crecimiento y la fisiología de la vid; pero no se destacó ninguna interacción entre WS y VI. Por el contrario, la combinación de los dos estreses subrayó una respuesta específica a nivel metabólico, no pudiéndose predecir cuantitativamente este efecto en base a la suma de cada uno de ellos. Los cambios observados en los metabolitos primarios se asociaron estrechamente con el metabolismo respiratorio. De hecho, el ajuste específico del metabolismo respiratorio (-i.e, cisteína, treonina, fumarato y eritronato 1,4-lactona) podría explicar potencialmente el mantenimiento del balance de carbono foliar y el crecimiento de las variedades estudias bajo condiciones de estrés combinado. En la presente tesis, hemos revelado la importancia de estudiar las interacciones vid-virus-estrés hídrico en condiciones de campo, particularmente en las variedades blancas donde las infecciones son asintomáticas y difíciles de identificar. Para completar este trabajo, sería interesante realizar un experimento con diferentes concentraciones de virus en un mayor número de cultivares y así confirmar si el efecto del virus depende de la concentración y/o si hay una diferencia en la susceptibilidad entre los cultivares.
Actualment, la producció agrícola mundial es troba limitada per una sèrie d‘estressos abiòtics i biòtics. A les zones de clima Mediterrani, s'espera que en un futur pròxim els esdeveniments de sequera siguin encara de major importància en termes d'intensitat, freqüència i durada. Per tant, en aquestes zones, el dèficit hídric és considerat com el principal factor ambiental capaç d‘afectar el creixement de la vinya. A més, la vinya es troba altament sotmesa a diferents virus, entre els quals, Grapevine leafroll-associated virus-3 (GLRaV-3) és un dels més estesos, provocant pèrdues econòmiques considerables a moltes vinyes d‘arreu del món. La identificació de com les diferents respostes a l‘estrès es troben integrades a la vinya i de com aquestes afecten el creixement i la fisiologia de les plantes és, per tant, de gran interès per a garantir la continuïtat del cultiu de la vinya. El primer objectiu d‘aquesta tesi tracta d‘estudiar l'estat sanitari dels cultivars minoritaris de vinya a Mallorca i destacar la prevalença a la vinya del virus GLRaV-3. Aquest estudi demostra una incidència d'infeccions víriques simples i múltiples (91,75%) molt alta en els cultivars locals de vinya, actualment conservats a la col·lecció de germoplasma de les Illes Balears. Sorprenentment, GLRaV-3 és el virus que més predomina en aquesta col·lecció (82%). Aquest resultat impulsa la necessitat d'una aplicació dràstica de tècniques de sanejament per tal d'obtenir plantes certificades lliures de virus. En aquest treball, s'han optimitzat dues tècniques de sanejament ―shoot tips culture and thermotherapy in combination with shoot tips culture‖ per a l'eradicació de virus dobles i triples a dos cultivars locals amb alt potencial enològic, Argamussa i Gorgollassa. El segon objectiu principal d‘aquesta tesi és estudiar els efectes de la infecció vírica, l'estrès hídric moderat i la seva combinació sobre els principals paràmetres fisiològics a dues varietats locals de vinya, Malvasia de Banyalbufar i Giró Ros. Cada un dels estressos estudiats, va resultar en un efecte negatiu sobre l'intercanvi de gasos a nivell foliar. L'estrès hídric a plantes sanes (WS-NI) va reduir de manera significativa el creixement de les plantes i l'assimilació neta al CO2 (AN), en canvi, sols va afectar lleugerament els canvis metabòlics, el que indicà que canvis sobre la AN durant l‘estrès hídric foren principalment deguts a les limitacions sofertes sobre determinats paràmetres difusius, com son la conductància estomàtica (gs) i la conductància del mesòfil (gm). A les plantes infectades per virus i cultivades sota condicions de reg (WW-VI), s‘obtingueren correlacions significatives entre els paràmetres fisiològics (AN, gs i gm), la concentració de virus i la presència de metabòlits. Aquestes correlacions varen desvelar que la presència de GLRaV-3 afectà la AN a través de limitacions difusives i no bioquímiques. En aquest cas, la conductància estomàtica es regí principalment pels canvis en la conductància hidràulica a nivell de la fulla (Kleaf) i el pecíol (Kpetiole), essent Kpetiole el paràmetre més rellevant alhora d‘estudiar l'efecte de virus floemàtics sobre el sistema hidràulic de la planta. Cal remarcar que els resultats obtinguts en aquest treball indiquen que la presència d‘un estrès combinat tingué un efecte negatiu sobre el creixement i la fisiologia de la vinya; però en cap cas es destacà una interacció entre WS i VI. Per contra, la combinació d‘ambdós estressos desencadenà una resposta específica a nivell metabòlic, que no va ser quantitativament predita per la suma dels dos. Els canvis observats en els metabòlits primaris varen resultar estar estretament associats amb el metabolisme respiratori. De fet, l'ajust específic del metabolisme respiratori (és a dir, cisteïna, treonina, fumarat i eritronat 1,4-lactona) podria explicar el manteniment de l'equilibri entre el balanç de carboni i el creixement en els dos cultivars estudiats. En el present treball, s‘ha avançat en quant a revelar quant d‘important és l‘estudi de les interaccions virus-estrès hídric a la vinya en condicions de camp, en particular, en els cultivars de raïm blancs on els efectes del virus són asimptomàtics i més difícils d'identificar. En un futur, es necessitaria aprofundir en aquest camp mitjançant la realització d‘estudis addicionals amb diferents concentracions víriques i un major nombre de cultivars per a ser capaços de confirmar si l'efecte del virus sobre la vinya depèn de la seva concentració i si cada cultivar presenta diferent susceptibilitat a la presència del virus.

Published Article
Alicyclobacillus acidoterrestris is a non-pathogenic, spore-forming bacterium that can survive the commercial pasteurisation processes commonly used during fruit juice production. Surviving bacterial endospores germinate, grow and cause spoilage of high acid food products. Fruit juices can be treated using ultraviolet light (UV-C) with a wavelength of 254 nm, which has a germicidal effect against micro-organisms. In this study, A. acidoterrestris was inoculated into water, used wash water from a fruit processing plant and grape juice concentrate. Ultraviolet dosage levels (J L-1) of 0, 61, 122, 183, 244, 305 and 367 J L-1 were applied using a novel UV-C turbulent flow system. The UV treatment method was shown to reliably achieve in excess of a 4 log10 reduction (99.99%) per 0.5 kJ L-1 of UV-C dosage in all the liquids inoculated with A. acidoterrestris. The applied novel UV technology could serve as an alternative to thermal treatments of fruit juices for the inactivation of Alicyclobacillus spores as well as in the treatment of contaminated wash water used in fruit processing.

A series of field, rainshelter, growth cabinet and modelling studies were conducted to investigate hot pepper response to different irrigation regimes and row spacings; to generate crop-specific model parameters; and to calibrate and validate the Soil Water Balance (SWB) model. Soil, climate and management data of five hot pepper growing regions of Ethiopia were identified to develop irrigation calendars and estimate water requirements of hot pepper under different growing conditions. High irrigation regimes increased fresh and dry fruit yield, fruit number, harvest index and top dry matter production. Yield loss could be prevented by irrigating at 20-25% depletion of plant available water, confirming the sensitivity of the crop to mild soil water stress. High plant density markedly increased fresh and dry fruit yield, water-use efficiency and dry matter production. Average fruit mass, succulence and specific leaf area were neither affected by row spacing nor by irrigation regimes. There were marked differences among the cultivars in fruit yields despite comparable top dry mass production. Average dry fruit mass, fruit number per plant and succulence were significantly affected by cultivar differences. The absence of interaction effects among cultivar and irrigation regimes, cultivars and row spacing, and irrigation regimes and row spacing for most parameters suggest that appropriate irrigation regimes and row spacing that maximize productivity of hot pepper can be devised across cultivars. To facilitate irrigation scheduling, a simple canopy cover based procedure was used to determine FAO-type crop factors and growth periods for different growth stages of five hot pepper cultivars. Growth analysis was done to calculate crop-specific model parameters for the SWB model and the model was successfully calibrated and validated for five hot pepper cultivars under different irrigation regimes or row spacings. FAO basal crop coefficients (Kcb) and crop-specific model parameters for new hot pepper cultivars can now be estimated from the database, using canopy characteristics, day degrees to maturity and dry matter production. Growth cabinet studies were used to determine cardinal temperatures, namely the base, optimum and cut-off temperatures for various developmental stages. Hot pepper cultivars were observed to require different cardinal temperatures for various developmental stages. Data on thermal time requirement for flowering and maturity between plants in growth cabinet and open field experiments matched closely. Simulated water requirements for hot pepper cultivar Mareko Fana production ranged between 517 mm at Melkassa and 775 mm at Alemaya. The simulated irrigation interval ranged between 9 days at Alemaya and 6 days at Bako, and the average irrigation amount per irrigation ranged between 27.9 mm at Bako and 35.0 mm at Zeway.
Thesis (PhD)--University of Pretoria, 2010.
Plant Production and Soil Science
unrestricted

Renewable energies are fluctuating and the bigger its share on the Swedish energy market, the more fluctuating are the prices. Therefore, CHP plant operators as VEAB in Växjö, are more and more struggling to be competitive. There is, hence, a need of alternative options for the use of produced electricity, rather than being dependent on such a volatile and unclear market. Hydrogen production through water electrolysis could therefore be an alternative to be decoupled from the electricity business and instead being part of a promising, future hydrogen economy. Since state-of-the-art electrolysers have efficiencies between 51% and 75%, it was assessed that some of the efficiency losses could be recuperated by implementing the excess heat in an existing District heating (DH) grid. Calculations of the base scenario electrolyser with a power input of 870 kW showed, that an increase of the overall temperatures of the returning mass flow of the DH grid from 0,05°C to 0,23°C should be achievable. The economic analysis showed, that for this size of hydrogen production unit, the minimum hydrogen selling price (MHSP) would be 6,64 €/kg, which is not competitive on today’s market. However, the sensitivity analysis showed, that by a decreased investment cost, lower electricity prices and especially by scaling up the base scenario, the MHSP could be lowered significantly. Assuming a reduction of investment costs of 20% and scaling up the electrolyser by 1000% to 8700 kW, the MHSP resulted in 1,9 €/kg, a competitive price on the market. This study revealed that hydrogen production could be part of the future business model of CHP plant operators and provides a guideline on the feasibility of such a project.

[Truncated abstract] In southern Western Australia the replacement of deep-rooted native vegetation with annual species has resulted in rising water tables and increased salinity due to insufficient water use. The area has a Mediterranean-type climate where rainfall during summer is generally low but variable resulting in limited plant growth. However, if rainfall does occur it potentially can contribute to to the increased water excess or drainage by increasing the soil water content before the main drainage period in winter. The first study investigated factors controlling soil water content changes during the fallow (December to May) in annual farming systems. This was achieved by examining variation in available soil water storage to a depth of 1.0-1.5 m at three sites within 13 seasons. Reasons for the variation were examined using the Agricultural Production Systems Simulator (APSIM). This study also investigated the relationship between soil water content at the end of the fallow period (1 May) and the amount of drainage below 2.5 m by using APSIM coupled to historical weather records at three locations. At the end of the fallow a mean of 24 mm (or 25%) of rainfall during the fallow was retained in the soil. Losses of soil water during the fallow were due to evaporation (mean of 60 mm), transpiration from plant cover (mean of 12 mm) and drainage below the root zone and run off (combined mean of 13 mm). Soil water accumulation during the fallow period had a significant impact on simulated drainage under wheat in the following growing season. Every 1 mm increase in soil wetness at the end of the fallow resulted in a 0.7-1 mm increase in simulated drainage during the growing season. ... Variation in the water excess due to variation in rainfall was greater than the reduction in water excess due to lucerne. This makes the decisions about when to grow lucerne to reduce water excess difficult if livestock enterprises are less profitable than cropping enterprises. The findings of this PhD indicate that lucerne does have a place in Mediterranean-type environments because of its greater water use than current farming practices. However, its use needs to be strategic and the strategy will vary from region to region. For example, in the low rainfall region lucerne sowings need to be matched with high soil water contents and phase length will generally be short (2-3 years). In comparison at high rainfall regions lucerne will need to be grown for longer or combined with other strategies to increase water use.

In horticultural sectors where water is a threatened resource, altering irrigation frequency may present a viable approach to reduce water use, without any negative effect on crop yield and/or quality. However, our understanding of the physiological impact of this approach in containers in a peat based substrate is limited. Pelargonium x hortorum Bullseye plants were grown in glasshouse conditions under well-watered (WW; daily replacement of 100% of evapotranspiration (ET)), frequent (FDI), or infrequent (IDI) deficit irrigation regimes (50% of ET supplied daily or cumulatively every 4 days, respectively) for four weeks. Both FDI and IDI resulted in short-term increases in water use efficiency, and longer term increases in plant quality (canopy compactness) compared to WW plants. From a physiological perspective, stomatal conductance (gs) decreased similarly under both FDI and IDI, but there were treatment differences in leaf water potential (Ψleaf). FDI resulted in a more positive Ψleaf compared to WW plants, whilst Ψleaf under IDI was typically the lowest. Given the lack of a consistent response for Ψleaf, this suggested another mechanism was regulating stomata in P.hortorum. Under a single drying cycle, different components of the xylem sap were measured. Xylem sap pH, Ca2+ and NO3 - did not change, but the plant hormone abscisic acid (ABA) increased in the xylem sap ([X-ABA]leaf) under both irrigation treatments as soil moisture decreased, and showed a strong relationship with gs both in vivo and in a detached leaf transpiration bioassay. However, when plants were irrigated daily at a percentage of daily ET (adapted from FDI), plants showed an attenuated ABA response compared to when irrigation was withheld (adapted from IDI). It was hypothesised that this may have been a root-derived response due to spatial variation in soil moisture distribution, which was investigated in tomato (Solanum lycopersicum). Similar results were found where gs decreased as [X-ABA]leaf increased, but again the ABA response was attenuated. Furthermore, stomata showed similar sensitivity to ABA under both irrigation treatments. However, similar results were found for root tissue ([ABA]root) and xylem ([X-ABA]root) ABA, and modelling revealed that both localised root water uptake and soil moisture content are important for explaining the variation in [X-ABA]root between irrigation treatments. This research furthers the fundamental understanding of ABA signalling and suggests that irrigation frequency can be altered for a short period of the growing cycle to deliver specific grower objectives.

Few elements in surface waters are monitored as closely as phosphorus (P) due to its role in the eutrophication and degradation of surface waters. Limiting P mobilization from source areas is, therefore, a central goal of water quality protection plans. But the work of locating sources in mixed-use watersheds is challenged by the spatial and temporal variability of critical source areas (CSAs) of P. Synoptic sampling is a proven method for capturing the spatial variation of water quality parameters in surface waters, though it's not often used to track temporal dynamics across the same study area. Phosphorus fractionation is an analytical method that divides the total P (TP) in water into fractions, which for this study included total dissolved P (TDP), particulate P (PP), dissolved reactive P (DRP), and dissolved organic P (DOP). The objective of this study was to demonstrate the utility of combining temporally repeated synoptic sampling with simple P fractionation as a unique strategy for locating and characterizing CSAs of P. Seven synoptic sampling campaigns were conducted over a two-year period (March 2015 – July 2016) in a rural, montane watershed in north central Utah, USA. In each campaign, we sampled 18 sites across three tributaries (Main Creek, Spring Creek, and Little Hobble Creek) during three distinct, annual hydrologic periods (rising flow, peak flow, and baseflow). Temporal repetition clearly identified the rising flow period as the period with greatest P loading in the watershed. Combining repeated synoptic sampling and P fractionation successfully identified CSAs of P and most probable transfer pathways. Specifically, stream segments along lower Spring Creek and Main Creek were associated with the greatest increases of PP loads during periods of rising flow and peak flow. In the same time periods, the greatest DOP loads stemmed from forested areas as well as areas in the lower watershed associated with winter grazing of cattle. The watershed exhibited a significant background concentration of DRP from groundwater-driven subsurface sources in the lower half of the watershed that persisted year-round. These assessments can be used to develop management practices that limit various P loads from these respective critical source areas. The characterization of CSAs could not have been made using only a traditional synoptic sampling approach. This study demonstrated that the combination of repeated synoptic sampling and P fractionation can be an effective technique for locating and characterizing critical P source areas in order to guide best management practices that improve surface water quality.

It is imperative to understand the strong coupling between the carbon capture process and water use to sustainably manage rangelands. Woody encroachment is undermining rangelands grass production. Evapotranspiration (ET) highlights the links between ecosystem carbon capture process and water use. It forms the biggest flux of the hydrological cycle after precipitation yet it is not well understood. The Grassland and the Albany Thicket (AT) biomes in the Eastern Cape, South Africa, provide an interesting space to study the dynamics in rangelands biomass production and the associated water use. Therefore, the main purpose of this study was to contribute towards management of rangelands by understanding the dynamics in rangeland grass production and water use. To achieve this aim, the impact of Acacia mearnsii, an invasive alien plant, on soil chemical properties and rangelands grass production was investigated. This was achieved by analysing the biophysical attributes of A. mearnsii as they related to grass production. Secondly, selected soil variables that could be used as a prognosis for landscape recovery or deterioration were evaluated. In addition, aboveground grass biomass was measured in areas cleared of A. mearnsii and regression equations were prepared to help model aboveground grass biomass in areas cleared of A. mearnsi. The thesis also explored dynamics in water vapour and energy fluxes in these two biomes using an eddy covariance system. Consequently, water vapour and energy fluxes were evaluated in order to understand landscape water use and energy partitioning in the landscape. The study also tested the application of Penman-Monteith equation based algorithms for estimating ET with micrometeorological techniques used for validation. Pursuant to this, the Penman- Monteith-Leuning (PML) and Penman-Monteith-Palmer (PMP) equations were applied. In addition, some effort was devoted to improving the estimates of ET from the PMP by incorporating a direct soil evaporation component. Finally, the influence of local changes in catchment characteristics on ET was explored through the application of a variant of the Budyko framework and investigating dynamics in the evaporative index as well as applying tests for trends and shifts on ET and rainfall data to detect changes in mean quaternary catchment rainfall and ET. Results revealed that A. mearnsii affected soil chemical properties and impaired grass production in rangelands. Hence, thinning of canopies provided an optimal solution for enhanced landscape water use to sequestrate carbon, provide shade, grazing, and also wood fuel. It was also shown that across sites, ET was water limited since differences between reference ET and actual ET were large. ET was largely sensitive to vapour pressure deficit and surface conductance than to net radiation, indicating that the canopies were strongly coupled with the boundary layer. Rangeland ET was successfully simulated and evaporation from the soil was the dominant flux, hence there is scope for reducing the so-called ‘unproductive’ water use. Further, it was shown that the PML was better able to simulate ET compared to the PMP model as revealed by different model evaluation metrics such as the root mean square error, absolute mean square error and the root mean square observations standard deviation ratio. The incorporation of a soil evaporation component in the PMP model improved estimates of ET as revealed by the root mean square error. The results also indicated that both the catchment parameter (w) and the evaporative index were important in highlighting the impacts of land cover change on ET. It was also shown that, despite changes in the local environment such as catchment characteristics, global forces also affected ET at a local scale. Overall, the study demonstrated that combining remote sensing and ground based observations was important to better understand rangeland grass production and water use dynamics.

The threatened Florida manatee (Trichechus manatus latirostris) migrates seasonally to warm-water refugia throughout the state of Florida due to metabolic requirements from low thermal conductance. Broward County’s two power plant refugia, Port Everglades (PEP) and Lauderdale (LPP), are known heavily-utilized aggregation sites for the Atlantic sub-population. Broward County collected relative abundance counts via aerial surveys from 2004–2013 siting 31,418 manatees during 169 surveys within 18 defined waterway zones. Counts during manatee wintering seasons were significantly different from January 2005-March 2008 and November 2008-March 2013, likely related to flight path and frequency standardization. Mean percentage of adults (90.12%) to calves (9.88%) demonstrates a higher usage by cow-calf pairs than other aggregation sites. Counts of manatees traveling south to Miami-Dade County comprised only 0.83% of all aerial counts, contrary to the theory of the extensive usage of Biscayne Bay foraging grounds. The LPP zone had 57.21% of all manatees with Port Everglades Inlet zone accounting for 23.88% and the South Fork New River zone with 5.95%. This study provided a baseline for pre-construction distributions prior to Port Everglades plant reenergization. With PEP construction now finished and LPP planned for reenergization in the next 10 years, monitoring data studies be compared to these baseline data to better assess the impact of the disruption of Broward County’s main refugia sources.

[Truncated abstract. Please see the pdf format for the complete text. Also, formulae and special characters can only be approximated here. Please see the pdf version for an accurate reproduction.] This thesis examines the water use, ecophysiology and hydraulic architecture of Eucalyptus marginata (jarrah) growing on bauxite mine rehabilitation sites in the jarrah forest of south-western Australia. The principal objective was to characterise the key environment and plant-based influences on tree water use, and to better understand the dynamics of water use over a range of spatial and temporal scales in this drought-prone ecosystem. A novel sap flow measurement system (based on the use of the heat pulse method) was developed so that a large number of trees could be monitored concurrently in the field. A validation experiment using potted jarrah saplings showed that rates of sap flow (transpiration) obtained using this system agreed with those obtained gravimetrically. Notably, diurnal patterns of transpiration were measured accurately and with precision using the newly developed heat ratio method. Field studies showed that water stress and water use by jarrah saplings on rehabilitation sites were strongly seasonal: being greatest in summer when it was warm and dry, and least in winter when it was cool and wet. At different times, water use was influenced by soil water availability, vapour pressure deficit (VPD) and plant hydraulic conductance. In some areas, there was evidence of a rapid decline in transpiration in response to dry soil conditions. At the end of summer, most saplings on rehabilitation sites were not water stressed, whereas water status in the forest was poor for small saplings but improved with increasing size. It has been recognised that mature jarrah trees avoid drought by having deep root systems, however, it appears that saplings on rehabilitation sites may have not yet developed functional deep roots, and as such, they may be heavily reliant on moisture stored in surface soil horizons. Simple predictive models of tree water use revealed that stand water use was 74 % of annual rainfall at a high density (leaf area index, LAI = 3.1), high rainfall (1200 mm yr-1) site, and 12 % of rainfall at a low density (LAI = 0.4), low rainfall (600 mm yr-1) site, and that water use increased with stand growth. A controlled field experiment confirmed that: (1) sapling transpiration was restricted as root-zone water availability declined, irrespective of VPD; (2) transpiration was correlated with VPD when water was abundant; and (3) transpiration was limited by soil-to-leaf hydraulic conductance when water was abundant and VPD was high (> 2 kPa). Specifically, transpiration was regulated by stomatal conductance. Large stomatal apertures could sustain high transpiration rates, but stomata were sensitive to hydraulic perturbations caused by soil water deficits and/or high evaporative demand. No other physiological mechanisms conferred immediate resistance to drought. Empirical observations were agreeably linked with a current theory suggesting that stomata regulate transpiration and plant water potential in order to prevent hydraulic dysfunction following a reduction in soil-to-leaf hydraulic conductance. Moreover, it was clear that plant hydraulic capacity determined the pattern and extent of stomatal regulation. Differences in hydraulic capacity across a gradient in water availability were a reflection of differences in root-to-leaf hydraulic conductance, and were possibly related to differences in xylem structure. Saplings on rehabilitation sites had greater hydraulic conductance (by 50 %) and greater leaf-specific rates of transpiration at the high rainfall site (1.5 kg m-2 day1) than at the low rainfall site (0.8 kg m-2 day1) under near optimal conditions. Also, rehabilitation-grown saplings had significantly greater leaf area, leaf area to sapwood area ratios and hydraulic conductance (by 30-50 %) compared to forest-grown saplings, a strong indication that soils in rehabilitation sites contained more water than soils in the forest. Results suggested that: (1) the hydraulic structure and function of saplings growing under the same climatic conditions was determined by soil water availability; (2) drought reduced stomatal conductance and transpiration by reducing whole-tree hydraulic conductance; and (3) saplings growing on open rehabilitation sites utilised more abundant water, light and nutrients than saplings growing in the forest understorey. These findings support a paradigm that trees evolve hydraulic equipment and physiological characteristics suited to the most efficient use of water from a particular spatial and temporal niche in the soil environment.