Dissertations / Theses on the topic 'Growth (Plants) Plant growing media'

Thesis (M.S.)--Worcester Polytechnic Institute.
Keywords: advanced life support; ethylene; carbon dioxide; pisum sativum; root hypoxia; oxygen; bioregenerative life support. Includes bibliographical references (p. 53-57).

Previous work has shown that despite the lack of oxygen limitation, transformed roots of Artemisia annua had lower biomass productivity in a nutrient mist bioreactor than in a liquid-phase bubble column reactor where the roots demonstrated metabolic signs of oxygen stress. Mathematical modeling suggested that the roots were too sparsely packed to capture mist particles efficiently and to achieve high growth rates. In this study, higher packing fractions were tested, and the growth rate increased significantly. Similarly, higher sucrose concentrations increased the growth rate. Growth kinetics for 2, 4, and 6 days showed an unexpected decrease or stationary growth rate after only 4 days for both 3% and 5% sucrose feeds. Residual media analyses indicated that carbon was not exhausted, nor were other major nutrients including phosphate. Increasing the misting frequency such that the total amount of carbon delivered from a 3% sucrose feed was equivalent to that delivered in a 5% sucrose feed showed that growth was affected by the modified cycle. These studies showed that both the concentration of carbon source and alteration of misting frequency can significantly increase growth rates of hairy roots in mist reactors.

The main objective of this study is to develop a modeling methodology that facilitates incorporating the plant pathway into environmental contamination models recognizing the fact that plants are dynamic entities that regulate their life cycle according to natural and anthropogenic environmental conditions. A modeling framework that incorporates the plant pathway into an integrated water flow and contaminant transport model in terrestrial systems is developed. The modeling framework is aimed to provide a tool to analyze the plant pathway of exposure to contaminants. The model developed using this framework describes the temporal and spatial variation of the contaminant concentration within the plant as it is interacting with the soil and the atmosphere. The first part of the study focuses on the integration of the dynamics of water and contaminant distribution and plant related processes within the vadose zone. A soil-plant system model is developed by coupling soil-water flow, contaminant transport, plant life-cycle, and plant pathway models. The outcome unifies single media continuous models with multimedia compartmental models in a flexible framework. The coupling of the models was established at multiple interfaces and at different levels of solution steps (i.e. model development phase vs. numerical solution phase). In the second part of the study, the soil-plant system model is extended to cover large spatial areas by describing the environmental system as a collection of soil-plant systems connected through overland flow and transport processes on the ground surface and through lateral interactions in the subsurface. An overland flow model is integrated with the previously coupled model of unsaturated zone soil-water flow and plant life-cycle by solving the flow model equations simultaneously within a single global matrix structure. An overland / subsurface interaction algorithm is developed to handle the ground surface conditions. The simultaneous solution, single-matrix approach is also adopted when integrating the overland transport model with the previously coupled models of vadose zone transport and plant pathway. The model developed is applied to various environmental contamination scenarios where the effect of the presence of plants on the contaminant migration within environmental systems is investigated.

Dissertation (PhD)--Stellenbosch University, 2004.
ENGLISH ABSTRACT: Pine sawdust-shavings (Pinus spp.) is at present a very popular soilless substrate in South African greenhouses. Growers use fresh pine sawdust-shavings as a substrate, which is biologically highly unstable. The greenhouse industry is looking at alternative organic substrates such as coco peat, which already went through a decomposition process and is more stable. A biological inactive substrate such as sand was included to compare microorganism activity with organic substrates. The main objective of this study was to compare the growth, yield and quality of hydroponically grown tomatoes in response to different growth mediums in combination with nitrogen source, irrigation frequency, period of substrate use and liming. In general the drainage water pH declined with an increase in NlLt+-N in the nutrient solution. Low pH values in the drainage water, especially when coco peat was used, had a detrimental effect on marketable yield. The drainage water pH of pine sawdustshavings increased during the growing season when 100 % N03--N was used. Due to the higher cation exchange capacity of coco peat, the drainage water electrical conductivity tends to increase more rapidly than with pine sawdust-shavings, during conditions with high temperatures and when insufficient irrigation volumes per irrigation cycle is applied. As expected the drainage water N03--N content decreased as the NlLt+-N content increased in the nutrient solution. Pine sawdust-shavings recorded a much lower N03--N and NlLt+-N content than sand and coco peat and thus supports the hypothesis that microbiological activity is higher in pine sawdustshavings, especially in the second season of substrate use. Coco peat produced the highest number of marketable fruit and yield per plant, followed by pine sawdustshavings and sand in the first season of substrate use. The number of marketable fruit and yield decreased with an increase in NlLt+-N content in the nutrient solution during production in warmer, summer conditions. Contrary to these fmdings, production in cooler, winter conditions recorded high yields when only N03--N or 80% N03--N : 20% NRt +-N was applied. The unmarketable yield increased with an increase in NlLt+-N in the nutrient solution. Visual evaluations showed that blossom-end rot (BER) was the main contributor to unmarketable yield. Increasing levels ofN03--N as nitrogen source in the nutrient solution, reduced weight loss and increased the loss of fruit firmness of tomatoes during storage. Increasing levels of N03 --N also increased fruit pH and reduced total titratable acidity. Coco peat produced fruit with a higher pH than pine sawdust-shavings. An increase in irrigation frequency affected fruit firmness negatively when coco peat was used as substrate. Different irrigation and fertigation practices are needed for different growth mediums and management needs to be adapted according to the growing season (winter vs. summer).
AFRIKAANSE OPSOMMING: 'n Mengsel van dennesaagsels en -skaafsels (Pinus spp.) word tans deur Suid- Afrikaanse kweekbuisprodusente gebruik as grondlose groeimedium. Hierdie groeimedium word nie vooraf gekomposteer nie en is dus biologies onstabiel. Die kweekbuisindustrie ondersoek tans die gebruik van alternatiewe, gekomposteerde en stabiele organiese groeimediums soos kokosveen. 'n Biologies onaktiewe groeimedium soos sand is ook ingesluit om met organiese groeimediums te kan vergelyk. Die hoof doelwit van die studie was om plantontwikkeling, opbrengs en kwaliteit van hidroponies geproduseerde tamaties te evalueer in verskillende groeimediums en in kombinasie met stikstofbron-verhouding, periode van groeimedium gebruik, besproeiingsfrekwensie en bekalking. Oor die algemeen het die pH in die dreinaat gedurende die groeiseisoen toegeneem soos die NH/-N inhoud verhoog het in die voedingsoplossing. Lae pH waardes in die dreinaat, veral waar kokosveen gebruik was, het 'n nadelige effek op bemarkbare opbrengs gehad. Die pH in die dreinaat van dennesaagsels en -skaafsels het gedurende die groeiseisoen toegeneem met die gebruik van 100% NO)--N in die voedingsoplossing. Die elektriese geleiding in die dreinaat van kokosveen neem vinniger toe gedurende toestande waarin hoë temperature en onder besproeiing voorkom, as in dreinaat van dennesaagsels en -skaafsels. Die NO)--N inhoud in die dreinaat het soos verwag afgeneem soos die NRt+-N inhoud in die voedingsoplossing toegeneem het. 'n Baie laer NO)--N en NRt+-N inhoud is by dennesaagsels en -skaafsels aangeteken wat dus die hipotese ondersteun dat mikrobiologiese aktiwiteit, veral in die tweede seisoen van gebruik, hoër is in dennesaagsels en -skaafsels as in sand en kokosveen. Kokosveen het die hoogste aantal bemarkbare vrugte en massa per plant geproduseer, gevolg deur dennesaagsels en -skaafsels en sand. Die aantal bemarkbare vrugte en opbrengs het verlaag met 'n verhoging in NRt+-N in die voedingsoplossing gedurende warm, somer toestande. In teenstelling met vorige resultate is gevind dat 100% NO)-- N of 80% NO)--N : 20% NRt+-N hoë opbrengste gelewer het gedurende koeler, winter toestande. Die onbemarkbare opbrengs het verhoog met hoër NRt+-N vlakke. Visuele waarnemings het aangedui dat blom-end verrotting die grootste bydrae tot onbemarkbare opbrengs gelewer het. 'n Verhoging in NO)--N vlakke het massaverlies beperk en die verlies in fermheid verhoog gedurende opberging. Hoër NO)--N vlakke het ook die pH van vrugte verhoog en die totale titreerbare suur verlaag. Kokosveen het vrugte met 'n hoër pH as dennesaagsels en -skaafsels geproduseer. 'n Toename in besproeiingsfrekwensie het vrug fermheid negatief beïnvloed wanneer kokosveen as groeimedium gebruik was. Verskillende besproeiings- en voedingspraktyke word benodig vir verskillende groeimediums en bestuur van die groeimediums moet aangepas word by klimaatstoestande gedurende die spesifieke produksieseisoen.

Mammalian estrogens and estrogen-like compounds known as xeno-estrogens are being found in and excreted into the environment in ever increasing amounts. The xeno-estrogen DDE has been found at high concentrations of 1-5 mg/kg of soil (Aislabie et. al, 1997). These estrogens and xeno-estrogens are having a devastating effect on animal-life, yet little is known or understood on the effects of estrogens on plant-life. Thus it is important to determine what effects (if any) estrogens may have on plants. Other research has shown that estrogen has an effect on plants grown in vitro (Janeczko and Skoczowski, 2005). This research aims to help increase the amount of information on what effects estrogens may have on plants. In this study, the effects of mammalian estrogens (17-β-estradiol, estrone and estriol) on the growth and tuberization of potato plants (Solanum tuberosum L. cv 'Iwa') grown in liquid tissue culture medium are presented. It was found that at even 0.1 mg/L of estrogen, root growth of the plants was diminished and at 10 mg/L of estrogen, plant deformity was apparent and callus growth induced. Acid phosphatase activity of the plants was increased with the addition of 0.1 mg/L and 1 mg/L of estrogen but then decreased with the addition of 10 mg/L of estrogen. Tuber production was slightly reduced in plants treated with estrogen compared to the control.

Effects of media, soil moisture, fertility rate, and plant growth regulators on plant growth were investigated for 13 taxa of succulents. Media: Liners were grown in five common greenhouse substrates: 80% peat, 60% bark + 30% peat moss, 80% pine bark/20% Permatil (v/v), 100% composted pine bark, or whole tree substrate until market ready. Overall, higher percentage bark mixes yielded smaller plants, with lower shoot dry weights, shoot heights and widths. Soil Moisture: Liners were potted into a 60% bark/30% peat soilless potting mix. In group 1 , irrigation to container capacity occurred when volumetric soil moisture content fell below 30%, 20%, or 10%,. Group two (seven species) irrigation thresholds were shifted to 35%, 25%, and 15%. Effects of irrigation rate were significant in three of the 13 species studied, and those effects were species-specific. Fertility Rate: Liners were potted into60% bark/30% peat substrate. Fertility reatments in group were 0, 50, 100, or 200 mg.L-1 nitrogen. Group 2 plants received treatments of 50, 150, 250, or 350 mg.L-1 nitrogen. Four of the 11 species studied were affected by nitrogen rate, with rates up to 200 mg.L-1 generally producing the largest plants. PGRs: Seven species were potted into a 60% bark/30% peat substrate. Group one plants were treated with a foliar application of benzyladenine (Configure) at rates of 0, 400, 800, or 1600 mg.L-1. Group 2 plants were treated either BA at 0, 250, 500, or 1000 mg.L-1, dikegulac sodium (Augeo) at 400, 800, or 1600 mg.L-1, or a tank mix of 500 mg.L-1 Configure and 800 mg.L-1 Augeo. BA caused an increase in branches leaders or offsets in two species.
Master of Science

Thesis (MTech (Horticultural Science))--Cape Peninsula University of Technology, 2016.
Hydroponics, i.e. plant cultivation in mineral-rich water is a synergy between plant, human, and machine. For decades the hydroponic garden has been offered on horticultural markets, and was repeatedly innovated to better meet consumer horticultural needs. Currently, platform convergences with electronic control systems can possibly enable more efficient products for direct consumer hydroponic cultivation. This means that, like many appliances in the home; hydroponic plant cultivation can become somewhat automated. Marketing and product innovation can help calibrate optimal New Product Development NPD of hydroponic gardens for people. The literature review grasps how consumers are subjected to a changing environment together with changing technology such as hydroponics, plant nutrition, and even garden automation. Market research frameworks namely Morphological Analysis (MA) and Conjoint Analysis (CA) are the tools deployed here for profiling and prioritising these products for horticultural consumers. Firstly, a qualitative analysis identifies conceptual sets for structures, inputs, and controls, which all harmonise into new intersections cultivation, hydroponics, and automation and the e-garden concepts. The MA next produces, and organises secondary data into constraints for the CA. Here, general hydroponic cultivation is first decomposed into all its many component parts which collectively describe the whole, where these parts are then classed along various attributes namely: garden plane xA, automation xB, performance xC, organics xD, and price xE So garden plane is composed of level and vertical gardens, garden automation is composed of manual and automatic gardens, garden performance is composed of casual and high-performance gardens, garden organics is composed of non-organic and organic gardens, and garden price although quantitative is simply composed of R2500 and R5000. These classes of attributed data can now become treated as categorical factors using indicator or dummy variables. Secondly, the CA determines how these attributes are most preferred by horticultural consumers at garden centre clusters. This involves measuring respondent preferences levels, to compute the part-worth utility for each attribute found in the MA. Factors such as garden organics, price, and automation hold adjusted alpha significance. Mainly, garden organics contributed to response effects, while price has negative slope and is second, while automation comes third. A combination of garden automation and organics is found to optimise consumer utility for Hydroponic Garden(s) HG.This research illuminates how horticultural consumers may prefer various HG, by understanding HG and how they can better benefit these people.

Red clover (Trifolium pratense L.) cvs 'Altaswede' (2n=2X=14) and 'Norseman' (2n=4X=28) were used in the present study to investigate tissue culture initiation, plant regeneration and the occurrence of somaclonal variation. Hypocotyl explants of aseptic seedlings were inoculated into L2 medium containing 0.06 mg/1 Picloram and 0.1 mg/1 benzyladenine for callus induction. Calli were usually induced after two weeks of culture. Callus induction frequency was 60% to 85% of the explants cultured with 'Altaswede' showing a slightly higher frequency than 'Norseman'. Satisfactory results were obtained under dark or light conditions using either test tubes or petri plates, as culture vessels. After callus induction, an experiment was conducted to regulate shoot induction by subculturing the calli on L2 medium containing 0.01 mg/1 2,4-dichlorophenoxy acetic acid and 2 mg/1 adenine (LSE) and on B₅ medium containing 2 mg/1 naphthalene acetic acid and 2 mg/1 adenine, media which have been reported to be shoot-supportive. However, both media failed to initiate shoots under the present experimental conditions. Further tests confirmed that LSE medium did not induce shoots from these calli and that callus growth on LSE medium steadily deteriorated over several subcultures. Subsequently, various media were tested with an emphasis on different combinations of growth regulators. Root differentiation from these calli was frequently observed. Shoots were initiated from some calli when they were transferred from SCP medium to media containing naphthalene acetic acid and kinetin. Embryogenic callus of one genotype was selected and maintained on LSP medium, leading to the regeneration of numerous plants. Supplementation with arginine, glutamic acid and casein hydrolysate did not show a significant effect on callus growth and differentiation. The source of callus influenced rates of growth and the occurrence of differentiation. Usually 'Norseman' calli grew faster and produced more roots than 'Altaswede' calli, while shoots were induced only from 'Altaswede' calli. Although 'Norseman' had more shoot tips induced to produce multiple shoots, the multiple shoot number per culture of 'Altaswede' was higher than that of 'Norseman'. Shoot tip cultures were also established to induce multiple shoots and to regenerate plants via root organogenesis. Regenerants from initial multiple shoots (RG1), multiple shoots after two subcultures (RG2), three-month calli (RG3) and one-year calli (RG4) were evaluated for chromosome number stability, morphology and several biochemical traits. When 'Altaswede' plants were analysed for chromosome number, RG1 and RG3 plants were normal, while one RG2 plant and 23% of 119 RG4 plants had tetraploid chromosome numbers. Regenerated plants were quite stable regarding their isozyme patterns of malate dehydrogenase, 6-phosphogluconate dehydrogenase, phosphoglucose isomerase, phosphoglucomutase and shikimate dehydrogenase and their nodule leghaemoglobin profiles. Morphologically, the leaflet length to width ratio of RG1, RG2 and RG3 plants of 'Altaswede' showed significantly more variation than control plants (P≤0.01), while RG4 plants of 'Altaswede' and RG1 and RG2 plants of 'Norseman' were not different from control plants. It is suggested that the absence of detectable differences in the RG4 'Altaswede' plants was a consequence of their origin from one original genotype. Variability and stability of regenerated plants are discussed.
Land and Food Systems, Faculty of
Graduate

Orientador: José Teixeira Filho
Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Geociências
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Resumo: O trabalho foi desenvolvido no campo experimental da Faculdade de Engenharia Agrícola da Universidade Estadual de Campinas, Campinas, SP, posição geográfica definida pelas coordenadas 22° 53' 22" LS e 47° 044' 39" LW. O estudo procurou verificar se a utilização de crostas de eletrofusão da bauxita como substrato, em leitos cultivados construídos ou "Constructeds Wetlands" com os vegetais aquáticos emergentes Typha sp, Canna limbata e Cyperus prolifer, interfere na dinâmica do pH, fósforo e nitrogênio presentes em águas residuárias domésticas. Foram utilizados 6 tanques artificiais, sendo constituído por 3 séries de duas unidades, com fluxo vertical e saídas subsuperficiais, nominados por série Typha, leitos 3.1 e 3.2; série Canna, leitos 2.1 e 2.2; série Cyperus 1.1 e 1.2 e preenchidos com crostas de eletrofusão da Bauxita. A dimensão de cada tanque é de 4 metros de comprimento por 3 metros de largura por 1 metro de altura, totalizando 12 m³. Em cada uma das séries foram plantados os vegetais Typha sp, Canna limbata e Cyperus prolifer respectivamente. O período de monitoramento foi de setembro de 2009 a fevereiro de 2010. O desempenho do foi avaliado considerando o desenvolvimento dos vegetais, quantidades e qualidades químicas das águas residuárias. As águas foram coletadas semanalmente, em dias aleatórios, nas entradas e saídas dos tanques durante o período monitorado; os vegetais foram colhidos, somente uma vez, no final do período. As vazões médias diárias e os pH médios ocorridos no período monitorado, observados no afluente e nas saídas da série Typha foram 962 l/dia, 864 l/dia e 804 l/dia; os pH foram 6,9; 8,6 e 9,0. Na série Canna as vazões foram 954 l/dia, 797 l/dia e 735 l/dia; os pH foram 6,9; 9,2 e 9,3. Na série Cyperus as vazões foram 792 l/dia, 723 l/dia e 664 l/dia; os pH foram 6,9; 9,0 e 9,1. Os tempos de detenções hidráulicas, considerando os leitos nas séries citadas foram: 4,2 dias e 4,6 dias; 4,0 dias e 4,6 dias e 4,3 dias e 4,4 dias. As porcentagens médias de retenções de nitrogênio total nos leitos, considerando as massas que entraram, por intermédio dos afluentes, durante o período monitorado foram: a) Série Typha 27% e 19%; b) Série Canna 35% e 19%; c) Série Cyperus 32% e 21%. As remoções realizadas pelos vegetais foram: a) Série Typha 26% e 9%; b) Série Canna 42% e 11%; Série Cyperus 22% e 15%. Em relação ao fósforo, as porcentagens médias de retenções, considerando as massas que entraram nos leitos por meio dos afluentes, foram: a) Série Typha 70% e 31%; b) Série Canna 73 e 19%; Série Cyperus 74% e 27%. As remoções realizadas pelos vegetais foram: a) Série Typha 11% e 4%; b) Série Canna 17% e 4%; c) Série Cyperus 7% e 11%. As massas vegetais totais secas produzidas foram: a) Série Typha 39,9 Kg e 11.2 Kg; b) Série Canna 50,5 Kg e 26,4 Kg; Série c) Cyperus 24 Kg e 15 Kg. O estudo mostrou que o substrato promoveu alterações na eficiência e eficácia da retenção e remoção de nutriente, crescimentos dos vegetais, produção de matéria seca e qualidades da água efluente
Abstract: The study was conducted in the experimental field of the Faculty of Agricultural Engineering, State University of Campinas, Campinas, SP, geographical position defined by coordinates 22° 53' 22" LS and 47° 04' 39" LW. The study examined whether the use of bauxite electrofusion crusts, as a substrate in constructed wetlands with emergent vegetables Typha sp, Canna limbata and Cyperus prolifer, interferes on the dynamics of pH, phosphorus and nitrogen present in domestic wastewater. It was used 6 artificial beds, consisting of 3 sets of two units with vertical flow and subsurface outflows, nominated by Typha series, 3.1 and 3.2 beds; series Canna, 2.1 and 2.2 beds, series Cyperus, 1.1 and 1.2 and filled with Bauxite electrofusion crusts. The size of each bed was 4 meters long by 3 meters wide by 1 meter high, totaling 12 m³. In each series the vegetables Typha sp, Canna limbata and Cyperus prolifer were planted respectively. The monitoring period was from September 2009 to February 2010. The performance was evaluated considering the development of plants, the chemical quantities and qualities of wastewater. The waters were collected weekly, on random days, at the entrances and exits of the beds during the monitoring period; the plants were harvested only once, at the end of each period. The average daily flow rates and average pH occurred during this period, observed in the tributary and the outflow of the series Typha were 962 l/day, 864 l/day and 804 l/day, the pH were 6.9, 8.6 and 9.0. In the series Canna flow rates were 954 l/day, 797 l/day and 735 l/day, the pH were 6.9, 9.2 and 9.3. In the series Cyperus flow rates were 792 l/day, 723 l/day and 664 l/day, the pH were 6.9, 9.0 and 9.1. The hydraulic detention time, considering the beds in the series cited were 4.2 days and 4.6 days, 4.0 days and 4.6 days and 4.3 days and 4.4 days. The average percentage of total nitrogen retention in the beds, considering the masses that came through the tributaries during the monitoring period was: a) Series Typha 27% e19% b) Series Canna 35% and 19%, c) Series Cyperus 32% and 21%. The removals conducted by the plants were : a) Series Typha 26% and 9%, b) Series Canna 42% and 11%; Series Cyperus 22% and 15%. Regarding the phosphorus, the average percentage of retention, considering the masses that entered the bed through the tributaries was: a) Series Typha 70% and 31%, b) Canna Series 73 and 19%; Series Cyperus 74% and 27 %. The removals conducted by the plant were: a) Series Typha 11% and 4%, b) Series Canna 17% and 4%, c) Cyperus Series 7% and 11%. The total dry plant mass produced were: a) Series Typha 39.9 Kg is 11.2 Kg b) Series Canna 50.5 kg is 26.4 kg; Series c) Cyperus 24 Kg is 15 Kg. The study has shown that the substrate promoted changes in the efficiency and effectiveness of nutrient removal and retention, growth of vegetables, dry material production and quality of effluent water
Mestrado
Análise Ambiental e Dinâmica Territorial
Mestre em Geografia

by Ng Ki Chi.
Thesis (M.Phil.)--Chinese University of Hong Kong, 1994.
Includes bibliographical references (leaves 130-145).
Acknowledgments
Abstract
Chapter Chapter 1 --- Introduction --- p.1
Chapter 1.1 --- Waste Management in Hong Kong --- p.1
Chapter 1.2 --- Sources of Organic Wastes and Their Characteristics --- p.4
Chapter 1.2.1 --- Animal manure --- p.5
Chapter 1.2.2 --- Sewage sludge --- p.7
Chapter 1.2.3 --- Food waste --- p.7
Chapter 1.3 --- Organic Waste Recycling --- p.9
Chapter 1.3.1 --- Organic wastes for land application --- p.9
Chapter 1.3.1.1 --- Animal manure --- p.11
Chapter 1.3.1.2 --- Sewage sludge --- p.12
Chapter 1.3.1.3 --- Plant residue --- p.14
Chapter 1.3.2 --- Composting --- p.15
Chapter 1.3.3 --- Biogas production --- p.16
Chapter 1.3.4 --- Organic wastes as feedstuffs or feed supplements --- p.18
Chapter 1.3.4.1 --- Animal manure --- p.18
Chapter 1.3.4.2 --- Sewage sludge --- p.19
Chapter 1.3.4.3 --- Plant residue --- p.20
Chapter 1.3.4.4 --- Biological products from waste conversion --- p.21
Chapter 1.4 --- Objectives and Outlines of the Present Study --- p.26
Chapter Chapter 2 --- Vermiculture of Eisenia foetida and Pheretima asciatica on Different Agro- industrial Wastes --- p.29
Chapter 2.1 --- Introduction --- p.29
Chapter 2.2 --- Materials and Methods --- p.34
Chapter 2.2.1 --- Collection of materials --- p.34
Chapter 2.2.2 --- Preparation of earthworms --- p.34
Chapter 2.2.3 --- Culture trial --- p.35
Chapter 2.2.4 --- Harvesting of earthworms --- p.35
Chapter 2.2.5 --- "Chemical analysis of bedding material, wastes and worm tissues" --- p.37
Chapter 2.2.6 --- Statistical analysis --- p.38
Chapter 2.3 --- Results and Discussion --- p.38
Chapter 2.3.1 --- Chemical properties of organic wastes and bedding material --- p.38
Chapter 2.3.2 --- Heavy metal contents in bedding material and organic wastes --- p.41
Chapter 2.3.3 --- Effects of organic wastes on worm growth --- p.43
Chapter 2.3.4 --- Effects of organic wastes on protein contents and protein yields --- p.47
Chapter 2.4 --- Conclusions --- p.49
Chapter Chapter 3 --- "Effects of Soybean Waste, Pig Manure and Digested Sludge on the Quality of Worm Meal From Eisenia foetida and Pheretima asciatica" --- p.53
Chapter 3.1 --- Introduction --- p.53
Chapter 3.2 --- Materials and Methods --- p.59
Chapter 3.2.1 --- Collection of materials --- p.59
Chapter 3.2.2 --- Preparation of earthworms --- p.59
Chapter 3.2.3 --- Experimental design and setup --- p.59
Chapter 3.2.4 --- Harvesting of earthworms --- p.61
Chapter 3.2.5 --- Chemical analysis of worm tissues --- p.61
Chapter 3.2.6 --- Statistical analysis --- p.63
Chapter 3.3 --- Results and Discussion --- p.63
Chapter 3.3.1 --- Effects of wastes on worm growth --- p.63
Chapter 3.3.2 --- Nutrient contents of earthworms from different wastes --- p.69
Chapter 3.3.3 --- Heavy metal contents in earthworm tissues --- p.72
Chapter 3.4 --- Conclusions --- p.81
Chapter Chapter 4 --- Worm Meal as Protein Source for Fish Diet --- p.82
Chapter 4.1 --- Introduction --- p.82
Chapter 4.2 --- Materials and Methods --- p.85
Chapter 4.2.1 --- Preparation of experimental diets --- p.85
Chapter 4.2.2 --- Feeding experiment --- p.88
Chapter 4.2.3 --- Chemical analysis --- p.90
Chapter 4.2.4 --- Statistical analysis --- p.90
Chapter 4.3 --- Results and Discussion --- p.90
Chapter 4.3.1 --- Growth response --- p.90
Chapter 4.3.1.1 --- Growth --- p.91
Chapter 4.3.1.2 --- Mortality --- p.95
Chapter 4.3.2 --- Tissue chemical composition --- p.95
Chapter 4.3.2.1 --- Nutritional contents --- p.97
Chapter 4.3.2.2 --- Heavy metal contents --- p.97
Chapter 4.4 --- Conclusions --- p.99
Chapter Chapter 5 --- Worm Worked Bedding as Potting Media for Plant Growth --- p.103
Chapter 5.1 --- Introduction --- p.103
Chapter 5.2 --- Materials and Methods --- p.106
Chapter 5.2.1 --- Preparation of potting media --- p.106
Chapter 5.2.2 --- Chemical analysis of potting media --- p.106
Chapter 5.2.3 --- Plant growth experiment --- p.107
Chapter 5.2.4 --- Tissue analysis --- p.109
Chapter 5.2.5 --- Statistical analysis --- p.109
Chapter 5.3 --- Results and Discussion --- p.109
Chapter 5.3.1 --- Chemical properties of potting media --- p.109
Chapter 5.3.2 --- Plant growth status --- p.114
Chapter 5.3.3 --- Heavy metal contents in plant tissues --- p.119
Chapter 5.4 --- Conclusions --- p.125
Chapter Chapter 6 --- General Conclusions --- p.126
References --- p.130

Cai Yi Jin.
Thesis (M.Phil.)--Chinese University of Hong Kong, 1993.
Includes bibliographical references (leaves 118-128).
Chapter 1. --- Introduction
Chapter 1.1 --- Importance and Cultivation history of edible mushroom --- p.1
Chapter 1.2 --- Variety and structure of growth substrates for mushroom --- p.4
Chapter 1.3 --- Mushroom growth and substrate-degrading enzymes --- p.8
Chapter 1.4 --- Purpose of study --- p.15
Chapter 2. --- Methods and Materials
Chapter 2.1 --- Organisms --- p.17
Chapter 2.2 --- Media --- p.17
Chapter 2.3 --- Culture conditions --- p.21
Chapter 2.3.1 --- Growth temperature --- p.21
Chapter 2.3.2 --- Growth Studies --- p.21
Chapter 2.3.2.1 --- Effect of pH on mycelial growth --- p.21
Chapter 2.3.2.2 --- Effect of different carbon sources on mycelial growth --- p.21
Chapter 2.3.2.3 --- Effect of lignin-related phenolic monomers and tannin derivatives on fungal growth --- p.22
Chapter 2.3.3 --- Culture conditions for production of extracellular enzymes --- p.23
Chapter 2.3.3.1 --- Tyrosinase --- p.23
Chapter 2.3.3.2 --- Laccase --- p.23
Chapter 2.3.3.3 --- Manganese-dependent Peroxidase and Lignin Peroxidase --- p.23
Chapter 2.3.3.4 --- Cellulytic and Xylanolytic enzymes --- p.24
Chapter 2.3.3.5 --- Lipase --- p.25
Chapter 2.3.4 --- Culture conditions for studying properties of cellulases of V. volvacea --- p.26
Chapter 2.3.4.1 --- CMCase --- p.26
Chapter 2.3.4.2 --- "CMCase, FPase and β-Glucosidase" --- p.26
Chapter 2.3.4.3 --- β-Glucosidase --- p.26
Chapter 2.4 --- Enzyme assay --- p.27
Chapter 2.4.1 --- Tyrosinase --- p.27
Chapter 2.4.2 --- Laccase --- p.27
Chapter a. --- o-Tolidine Method --- p.27
Chapter b. --- ABTS Method --- p.28
Chapter c. --- Syringaldazine Method --- p.28
Chapter 2.4.3 --- Lignin peroxidase --- p.29
Chapter 2.4.4 --- Manganese-dependent peroxidase --- p.29
Chapter 2.4.5 --- Exoglucanase (avicelase) --- p.30
Chapter 2.4.6 --- Endoglucanase (carboxymethylcellulase or CMCase) --- p.31
Chapter 2.4.7 --- Filter paper digesting enzyme (FPase) --- p.32
Chapter 2.4.8 --- P-Glucosidase --- p.32
Chapter 2.4.9 --- Xylanase --- p.34
Chapter 2.4.10 --- β-Xylosidase --- p.34
Chapter 2.4.11 --- Lipase --- p.36
Chapter 2.5 --- Other analytical methods --- p.36
Chapter 2.5.1 --- Determination of phenol oxidase activity by the Bavendamm reaction --- p.36
Chapter 2.5.2 --- Qualitative evaluation of CMCase by Congo red staining --- p.37
Chapter 2.5.3 --- Effect of phenolic monomers and tannic acid on CMCase activity of V. volvacea --- p.38
Chapter 2.5.4 --- Protein determination --- p.39
Chapter 2.5.5 --- Non-denaturing gel electrophoresis pattern of fungal laccases --- p.39
Chapter 2.6 --- Chemicals --- p.39
Chapter 3. --- Results
Chapter 3.1 --- Growth and Nutritional characteristics --- p.44
Chapter 3.1.1 --- Fungal growth on defined and non-defined culture media --- p.44
Chapter 3.1.2 --- Effect of carbon source on fungal --- p.45
Chapter 3.1.3 --- Effect of pH on fungal growth --- p.45
Chapter 3.2 --- Effect of lignin-related phenolic monomers and tannin derivatives on fungal growth --- p.45
Chapter 3.2.1 --- Effect of lignin-related phenolic monomers on fungal growth --- p.45
Chapter 3.2.2 --- Effect of tannin derivatives on fungal growth --- p.61
Chapter 3.3 --- Phenol Oxidase --- p.67
Chapter 3.3.1 --- Phenol oxidase --- p.67
Chapter 3.3.1.1 --- Guaiacol-reacting enzyme --- p.67
Chapter 3.3.1.2 --- o-Anisidine oxidizing enzyme --- p.68
Chapter 3.3.2 --- Tyrosinase --- p.69
Chapter 3.3.3 --- Laccase --- p.69
Chapter 3.3.3.1 --- "Laccase detected by o-Tolidine, ABTS Syringaldazine" --- p.69
Chapter 3.3.3.2 --- Effect of pH on laccase activity --- p.69
Chapter 3.4 --- Lignin-Transforming Enzymes --- p.73
Chapter 3.4.1 --- Lignin peroxidase (LP) --- p.73
Chapter 3.4.2 --- Manganese-dependent peroxidase (MnP) --- p.74
Chapter 3.5 --- Cellulases --- p.78
Chapter 3.5.1. --- Cellulases of V. volvacea --- p.78
Chapter 3.5.1.1 --- Qualitative estimation of cellulose-degrading enzymes of V. volvacea grown on different substrates --- p.78
Chapter 3.5.1.2 --- Influence of pH and temperature --- p.79
Chapter 3.5.1.3 --- Cellulolytic activities in cultures grown on cellulose --- p.83
Chapter 3.5.1.4 --- Cellulolytic activities in cultures grown on paddy straw --- p.91
Chapter 3.5.1.5 --- β-Glucosidase activity in cultures grown on cellobiose --- p.91
Chapter 3.5.1.6 --- Effect of lignin-related phenolic monomers and tannic acid on CMCase of V. volvacea --- p.95
Chapter 3.5.2 --- Cellulases of P.sajor-caju --- p.96
Chapter 3.5.3 --- Cellulases of L. edodes --- p.96
Chapter 3.6 --- Xylanase --- p.96
Chapter 3.6.1 --- "Xylanase of V. volvacea, strain V34" --- p.96
Chapter 3.6.2 --- Xylanase of P.sajor-caju --- p.100
Chapter 3.6.3 --- Xylanase of L. edodes --- p.100
Chapter 3.7 --- Lipase of V. volvacea --- p.103
Chapter 4. --- Discussion
Chapter 4.1. --- Carbon nutrition and pH for fungal growth --- p.104
Chapter 4.1.1 --- Carbon nutrition --- p.104
Chapter 4.1.2 --- pH --- p.104
Chapter 4.2 --- "Effect of lignin-related phenolic monomers and tannin derivatives on fungal growth of L. edodes, P. sajor-caju and V, volvacea" --- p.105
Chapter 4.2.1 --- Lignin-related phenolic monomers --- p.105
Chapter 4.2.2 --- Tannin derivatives --- p.107
Chapter 4.3 --- "Production of phenoloxidases by V. volvacea, L. edodes and P. sajor-caju" --- p.108
Chapter 4.3.1 --- Guaiacol- and Anisidine reacting enzymes and Tyrosinase --- p.108
Chapter 4.3.2 --- Laccase --- p.109
Chapter 4.4. --- "Lignin-degrading Enzymes of V. volvacea, P. sajor-caju and L. edodes" --- p.110
Chapter 4.5. --- "Cellulolytic and Hemicellulolytic Activity of V. volvacea, P.sajor-caju and L. edodes" --- p.113
References --- p.118
Appendix1 --- p.129

Peat extraction for horticultural production poses a threat to wetland ecosystems. The rapid growth rate of the horticulture industry has prompted an ongoing search for sustainable alternative growth media components to replace peat. The alternative components need to provide properties (physical and chemical) similar to or better than peat and provide conditions that will enhance ideal growth and yield of potted plants. Potted Dendranthema x grandiflorum is one of the most important pot plants cultivated worldwide in the floriculture industry. There is a global research effort to replace peat with a sustainable alternative growth media for potted plants; however, so far, no study has been conducted in South Africa that used similar treatments on potted Dendranthema x grandiflorum. The aim of this study was to determine a suitable alternative growth media to replace peat as a growth media for cultivation of potted D. x grandiflorum. A greenhouse experiment was conducted at the University of South Africa’s Horticulture centre in Florida, Johannesburg for 89 days. Eight growth media (100 % peat (T1) (control), 100 % bagasse (T2), 50:50 % v/v bagasse:peat (T3), 75:25 % v/v bagasse:peat (T4), 25:75 % v/v bagasse:peat (T5), composted bagasse (T6), Coir (T7), and pine bark (T8)) as treatments and one hybrid (Mount® Runca) of D. x grandiflorum were arranged in a randomized complete block design with four replicates. In this study, nutrient uptake, chlorophyll content, growth, and yield parameters were measured for potted D. x grandiflorum grown in all eight growth media. The results show that treatments had different chemical and physical properties compared to peat. The pH of 100 % bagasse and coir were within the ideal range recommended for growth media. The EC results indicated that after the experiment, other treatments were within the defined range except for composted bagasse due to high concentration of soluble salts. The BD of control and composted bagasse were similar and may have resulted in the low root response. The concentration of total N was high in the shoots of plants cultivated in 100 % peat with a subsequent increased fresh and dry shoots weight. The highest significant chlorophyll content was present in plants cultivated in composted bagasse, which contained high total N and, Fe and Zn concentrations in shoots. Taken together, the results showed that composted bagasse was the best alternative to replace peat for cultivation of potted D. x grandiflorum.
Turfonttrekking vir tuinboukundige produksie hou ʼn bedreiging vir moerasland-ekostelsels in. Die vinnige groeitempo van die tuinboubedryf het gelei tot ʼn voortdurende soektog na volhoubare groeimediakomponente om turf te vervang. Die alternatiewe komponente moet (fisiese en chemiese) eienskappe kan bied wat soortgelyk aan, of beter as dié van turf is, en moet toestande gee wat die ideale groei en opbrengs van potplante verbeter. Potplant- Dendranthema x grandiflorum is een van die belangrikste potplante wêreldwyd wat in die blomboerderybedryf aangeplant word. Daar word wêreldwyd navorsing gedoen om turf met ʼn volhoubare groeimedium vir potplante te vervang; sover is daar egter nog nie in Suid-Afrika ʼn studie gedoen wat soortgelyke behandelings vir potplante- Dendranthema x grandiflorum gebruik nie. Die doel van hierdie studie was om ʼn gepaste alternatiewe groeimedium te bepaal om turf as ʼn groeimedium te vervang vir die aanplanting van D. x grandiflorum-potplante. ʼn Kweekhuis-eksperiment is by die Universiteit van Suid-Afrika se Tuinbousentrum in Florida, Johannesburg uitgevoer vir 89 dae. Agt groeimedia (100% turf (T1) (beheer), 100% bagasse (T2), 50:50% v/v bagasse:turf (T3), 75:25% v/v bagasse:turf (T4), 25:75 % v/v bagasse:turf (T5), bagasse wat tot kompos verwerk is (T6), klapperhaar (T7), en dennebas (T8)) as behandelings en een hibried (Mount® Runca) van D. x grandiflorum is in ʼn verewekansigde, volledige blokontwerp met vier repliserings gerangskik. In hierdie studie is voedingstofopname-, chlorofilinhoud-, groei- en opbrengs-parameters gemeet vir potgroei van D. x grandiflorum in al agt groeimedia. Die resultate toon dat die behandelings verskillende chemiese en fisiese eienskappe in vergelyking met turf het. Die pH van 100% bagasse en klapperhaar val binne die ideale reikwydte wat vir groeimedia aanbeveel word. Volgens die EG (elektriese geleiding)-resultate was ander behandelings binne die gedefinieerde reikwydte – behalwe vir bagasse wat tot kompos verwerk is – vanweë die hoë konsentrasie oplosbare soute. Die BD van beheer en bagasse wat tot kompos verwerk is, was soortgelyk en kon die lae wortelrespons veroorsaak het. Die konsentrasie totale N was hoog in die lote van plante wat in 100% turf aangeplant is, met ʼn gevolglike verhoging in die gewig van vars en droë lote. Die hoogste beduidende chlorofilinhoud was teenwoordig in plante wat gekweek is in bagasse wat tot kompos verwerk is, en wat hoë totale konsentrasies van N, Fe en Zn in die lote bevat het. Alles in ag genome het die resultate getoon dat bagasse wat tot kompos verwerk is, die beste alternatief is om turf te vervang in die kweking van D. x grandiflorum in potte.
Go ntsha borubu mo kumong ya mokgwa wa temo go na le matshosetsi mo matshelong a diphologolo le ditlhare tsa lefatshe le le kolobileng. Kelo ya kgodiso e e bonako ya intaseteri ya matshelo a diphologolo le ditlhare e susumetsa patlo e e tswelelang ya dikarolo tsa mekgwa ya kgodiso ya thefosano e e tswelelang ya go emela go ntsha borubu. Dikarolo tse dingwe di tlhoka go neela dipharologantsho (sebopego le khemikale) tse di tshwanang le kgotsa botoka mo go ntsheng borubu le go neela mabaka a a ka tsholetsang kgodiso e e ikaeletsweng, mme ya ntsha dijalo tse di ka fa dipitseng. Dendranthema x grandiflorum e e ka fa dipitseng ke thefosano nngwe ya dijalo tsa ka fa dipitseng tse di botlhokwa thata tse di jadilweng mo lefatsheng ka bophara mo intasetering ya mokgwa wa temo ya dithunya. Go na le boiteko jwa patlisiso ya bogotlhe ya go emela go ntsha borubu ka mokgwa wa kgodiso wa thefosano o mongwe o o tswelelang wa dijalo tsa ka fa dipitseng; le gale, go le kalo, ga go na thuto e e setseng e dirilwe mo Aforikaborwa e e dirisang ditshwaro tse di tshwanang mo go Dendranthema x grandiflorum e e mo dipitseng. Maikaelelo a thuto eno e ne e le go tlhomamisa mekgwa ya grandiflorum e e mo dipitseng. Maikaelelo a thuto eno e ne e le go tlhomamisa mekgwa ya kgodiso ya thefosano e mengwe e e tshwanelang go emela go ntsha borubu jaaka mekgwa ya kgodiso ya go jala D. x grandiflorum ka mo dipitseng. Tekelelo ya ntlo e tala e ne ya dirwa kwa lefelong la Mokgwa wa matshelo a diphologolo le ditlhare ya Yunibesiti ya Aforikaborwa kwa Florida, Johannesburg mo matsatsing a le 89. Mekgwa ya kgodiso e merobedi (100 % ya go ntsha borubu (T1) (taolo), 100 % bagasse (T2), 50:50 % v/v bagasse: go ntsha borubu (T3), 75:25 % v/v bagasse: go ntsha borubu (T4), 25:75 % v/v bagasse: go ntsha borubu (T5), bagasse e e bodisitsweng (T6), Coir (T7), le kutu ya phaene (T8)) jaaka ditshwaro le lotswakwa lo lo longwe (Mount® Runca) ya D. x grandiflorum di ne di beilwe ka moakanyetso wa boloko e e feletseng ka kakaretso ka ditshwano di le nne. Mo thutong eno, go tsaya kotlo, diteng tsa setalafatsi, kgodiso le diparametara tse di ntshitsweng di ne tsa lekanyediwa mo go D. x grandiflorum e e mo dipitseng e e jadilweng mo mekgweng ya dikgodiso tse di robedi tse tsotlhe. Dipheto di bontsha gore ditshwaro di na le dikarolo tsa dikhemikale le dibopego tse di farologaneng fa di tshwantshanngwa le go ntsha borubu. Bagasse ya pH ya 100 % le coir di ne di le magareng ga paka ya botlhokwa ya kgodiso e e atlenegisitsweng mo mekgweng ya kgodiso. Dipheto tsa EC di bontsha gore morago ga tekelelo, ditshwaro tse dingwe di ne di le magareng ga paka e e tlhalositsweng kwa ntle ga bagasse e e bodisitsweng kwa kokoanong e e kwa godimo ya matswai a a tlhaolositsweng. BD ya taolo le bagasse e e bodisitsweng, mme go ka bo go dirile gore go nne le tsibogelo ya medi e e kwa tlase. Kokoano ya N yotlhe e ne e le kwa godimo mo matlhogeding a dijalo tse di jadilweng ka go ntsha borubu jwa 100 % ka koketso e e latelang ya bokete jwa matlhogedi a mantshwa le a a omileng. Diteng tsa setalafatsi se se botlhokwa se se kwa godimodimo di ne di le teng mo dijalong tse di jadilweng ka bagasse e e bodisitsweng, e e nang le kokoano ya bogotlhe jo bo kwa godimo jwa N, Fe le Zn mo matlhogeding. Di tserwe mmogo, dipheto di bontsha gore bagasse e e bodileng jaaka sengwe se se gaisang go emela go ntsha borubu mo jalong ya D. x grandiflorum ka mo dipitseng.
School of Environmental Sciences
M. Sc. (Ornamental Horticulture)

The tomato is one of the most important vegetable crops grown in the South African community. Most hydroponic tomato growers in South Africa are using sawdust as a growing medium due to its availability and affordability. However, there is little or no information on how particle sizes of sawdust influence tomato yield and quality. The aim of the study was to determine the effect of the particle size of sawdust on plant growth, yield and quality of tomato. Six treatments of different particle sizes of sawdust i.e. fine (F), medium (M), coarse (C) and 50:50 ratio of F: M, C: M, and C: F extracted from pine tree were used for the experiment. Treatments were arranged in a randomized complete block design with four replicates. The size of the sawdust particles did not have a significant effect on plant height, stem diameter, leaf length and width, shelf-life, marketable yield, total yield and unmarketable yield. A tendency to increase marketable and total yield was observed when tomato plants were grown at a 50:50 C: F ratio. Fruit and leaf mineral content were not affected by sawdust particle size. After completion of the experiment, air- filled porosity was significantly high on particle size C, M, and C: M while the water holding capacity was significantly high on F followed by M. The study showed that the suitable growth medium for production of tomatoes under the hydroponics system used was the CF particle substrate. Generally, the experimental crop performed better under the CF particle substrate in terms of growth parameters, and fruit quality, thus leading to the conclusion that the CF growth medium is ideal for hydroponically grown tomato under a non-environmentally controlled polytunne
Agriculture, Animal Health and Human Ecology
M. Sc. (Agriculture)

Micropropagation of Aloe polyphylla, an endangered species with a high ornamental and medicinal value, is an important part of its conservation. However, the in vitro culture was hindered by the phenomenon of hyperhydricity. The research reported in this thesis was undertaken for two reasons. Firstly, to understand the role of various culture factors involved in the process of hyperhydricity in A. polyphylla and to identify the in vitro conditions, under which this disorder can be prevented. Secondly, we conducted an investigation into the underlying mechanisms of this phenomenon by probing if it was mediated through internal cytokinins. Ammonium (NH4 +) ions, applied cytokinins (CKs) and CK concentrations were tested in multifactorial combinations and significantly influenced the regeneration rate and occurrence of hyperhydricity. Shoots were grown on media with different NH4 + concentrations (10.3, 20.6 and 61.8 mM) and supplemented with BA, zeatin or TDZ at 0, 5 or 15 ìM. Elevating the levels of NH4 +, in the absence of CKs, could not induce hyperhydricity. Similarly, very low hyperhydricity was observed when CKs were added to media containing low NH4 + (10.3 mM). However, in the presence of higher NH4 + concentrations, CKs increased hyperhydricity in a concentrationdependant manner, suggesting that they were capable of inducing this syndrome only when other factors in the culture system were not optimised. High numbers of healthy looking shoots were produced on media with low NH4 + and low BA or zeatin (5 ìM). The use of TDZ resulted in the formation of buds, which did not develop into shoots. In view of the fact that NH4 + was supplied in the form of NH4NO3, it was difficult to determine if NH4 + or nitrate (NO3 -) ions were associated with the increase in hyperhydricity. We further examined the role of nitrogen (N) supplied as inorganic NH4 + or NO3 -, or organic glutamine. The omission of total N from the culture medium resulted in low multiplication and hindered shoot growth. Ammonium as the sole source of N depressed shoot regeneration and growth and escalated the frequency of hyperhydricity to ca. 50%. When NO3 - was used as the sole N source, shoots of fine quality were produced and hyperhydricity was completely eliminated. Overall, the MS N mix was superior to any single N source for multiplication and growth of shoots, suggesting a synergistic effect between NH4 + and NO3 - on shoot regeneration. Furthermore, not only the absolute amount of N, but also the relative amounts of NH4 + and NO3 - influenced the multiplication rate, frequency of hyperhydricity and shoot quality. The highest regeneration was obtained with NH4 + : NO3 - ratios (mM) of 20 : 40, 30 : 30 and 40 : 20. Decreasing the ratio of NH4 + : NO3 - lowered the occurrence of hyperhydricity. The potential of glutamine as the sole source of N was also demonstrated, since its application resulted in the production of good quality shoots and almost no hyperhydricity. Shoot explants grown in static liquid media became hyperhydric and lost their ability to regenerate. The type of gelling agent used to solidify the medium affected greatly hyperhydricity and shoot multiplication. Gelrite resulted in a significantly lower multiplication rate and four times higher hyperhydricity (64.7%) compared to when agar was used. Gelrite was further selected to test the hypothesis if hyperhydricity can be overcome by decreasing the relative matric potential of the media, and respectively the availability of water, as represented by increasing gelrite concentrations. Satisfactory reduction in hyperhydricity was achieved only at 16 g l-1 gelrite, however the regeneration also decreased. The nature of the gelling agent is therefore essential for the successful control of this phenomenon. It appears that a crucial prerequisite for the reduction of hyperhydricity in tissue cultures of A. polyphylla is the gaseous exchange between the in vitro atmosphere and the outside environment. In ventilated cultures, achieved by using a modified lid with a hole (d = 7 mm) covered with polyester or cotton mesh, hyperhydricity was completely eliminated, irrespectively of the type of gelling agent. Ventilation was further advantageous for the in vitro regenerants by increasing their leaf chlorophyll content as well as epicuticular wax deposition, the last one being indicative of the development of the water loss regulation mechanisms of explants. The increased culture ventilation, however, was negatively correlated with the regeneration rate and shoot growth. Endogenous CKs were measured in in vitro regenerants after an eight-week cycle to examine whether the hyperhydricity-inducing effect of exogenous CKs and gelling agents is associated with changes in the endogenous CK content. The content of endogenous CKs, determined by HPLC-mass spectrometry, in the shoots grown on CK-free media comprised isopentenyladenine-, trans-zeatin- and cis-zeatin-type CKs. The application of exogenous CKs resulted in an increase in the CK content of the shoots. Following application of zeatin, dihydrozeatin-type CKs were also detected in the newly-formed shoots. Application of BA to the media led to a transition from isoprenoid CKs to aromatic CKs in the shoots. Shoots grown on gelrite media contained higher levels of endogenous CKs compared to those on agar media. Total CK content of hyperhydric shoots was higher than that of normal shoots grown on the same medium. We suggest that the ability of exogenous CKs and gelrite to induce hyperhydricity in shoots of Aloe polyphylla is at least partially due to up-regulation of endogenous CK levels. However, hyperhydricity is a multifactor process in which different factors intervene.
Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2009.