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1
Beardsell, DV, RB Knox, and EG Williams. "Germination of Seeds From the Fruits of Thryptomene calycina (Myrtaceae)." Australian Journal of Botany 41, no. 2 (1993): 263. http://dx.doi.org/10.1071/bt9930263.
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Freshly fallen fruits of T. calycina contained seeds which were completely dormant; none germinated after 200 days at 20°C. Seeds excised with testas intact from fresh fruits were partially dormant; one-third germinated after 60 days. The dormancy of seeds in freshly fallen fruits was imposed jointly by the fruit and the seed. The major site of the dormancy was however the seed coat since tearing part of it away from seeds excised from fresh fruits resulted in rapid and complete germination. Fruits stored dry in a laboratory at 20°C for 90 days were partially dormant. Nicking the distal end of these fruits enhanced germination. Seeds excised from these laboratory stored fruits had 85 % germination, which indicated a reduction in the seed imposed dormancy. Germination of T. calycina was independent of light and, although the fruits contained large amounts of phenolic material this did not inhibit germination. Fruits weathered in the field for at least 2 years contained less viable seeds, presumably because of insect predation, but these all germinated within 50 days at 20°C. Brief washing of fruits in concentrated sulphuric acid increased germination. Germination was not enhanced by treatment with low concentrations of gibberellic acid in the presence or absence of cytokinin.
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Silveira, Fernando A. O., Rafaella C. Ribeiro, Denise M. T. Oliveira, G. Wilson Fernandes, and José P. Lemos-Filho. "Evolution of physiological dormancy multiple times in Melastomataceae from Neotropical montane vegetation." Seed Science Research 22, no. 1 (October 18, 2011): 37–44. http://dx.doi.org/10.1017/s0960258511000286.
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AbstractWe investigated seed dormancy among species of Melastomataceae from Neotropical montane vegetation of Brazil. Four out of 50 studied species had dormant seeds:Miconia corallina(Miconieae), Tibouchina cardinalis(Melastomeae), Comolia sertularia(Melastomeae) andChaetostoma armatum(Microlicieae). For these four species, germinability of seeds collected in different years was always < 10% and the percentages of embryoless seeds and non-viable embryos were both insufficient to explain low or null germinability. This is the first unequivocal report of seed dormancy in tropical Melastomataceae. The production of seeds with permeable seed coats and fully developed, differentiated embryos indicates the occurrence of physiological dormancy. The reconstructed phylogenetic tree of the 50 species suggests that physiological dormancy evolved multiple times during the evolutionary history of Melastomataceae in this vegetation. Physiological dormancy evolved in species and populations associated with xeric microhabitats, where seeds are dispersed in unfavourable conditions for establishment. Therefore, drought-induced mortality may have been a strong selective pressure favouring the evolution of physiological dormancy in Melastomataceae. We argue that dormancy may have been independently selected in other lineages of Cerrado plants colonizing xeric microhabitats and dispersing seeds at the end of the rainy season. The contributions of our data to the understanding of seed dormancy in tropical montane vegetation are discussed.
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FRÉGEAU, JUDITH A., and VERNON D. BURROWS. "SECONDARY DORMANCY IN DORMOATS FOLLOWING TEMPERATURE TREATMENTS: FIELD AND LABORATORY RESPONSES." Canadian Journal of Plant Science 69, no. 1 (January 1, 1989): 93–99. http://dx.doi.org/10.4141/cjps89-011.
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Partially after-ripened seeds of three dormoat lines (Avena sativa L. × A. fatua L.) were treated to induce secondary dormancy before field planting in the fall. The objectives of this experiment were to evaluate the dormancy response of the treated seeds and to determine if field performance, in terms of both survival and emergence, was improved by the treatments. Treatments consisted of imbibition and incubation of seeds at two temperatures: 4 °C for 3 wk or 30 °C for 2 wk. Both treatments increased dormancy, but differences were also noted in the type of relative dormancy expressed by each seed population under laboratory conditions. Treated seeds and the appropriate untreated control seeds were sown in the field, in fiberglass mesh bags, either in early or late fall depending on the treatment. Levels of dormant seeds retrieved from the field, at the end of the fall season, varied for each dormoat line and did not reflect the induced secondary dormancy measured before field planting. The fate of these dormant seeds after exposure to winter stresses was assessed on field-retrieved material in the spring. In relation to a late sowing of untreated seeds, the treatments were effective in improving levels of viable seeds (dormant or germinating) remaining in the ground, in the spring. However, the best performance, both in survival and emergence, was obtained with an early fall planting of untreated seeds. High loss of viability was common to both treated and untreated seeds of the three dormoat lines. The major shortcoming of dormoats seems to be in the area of cold resistance of the fall dormant seeds since damage during winter played an important role in survival.Key words: Secondary dormancy, relative dormancy, dormoats, emergence
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Cohn, Marc Alan. "Operational and philosophical decisions in seed dormancy research." Seed Science Research 6, no. 4 (December 1996): 147–54. http://dx.doi.org/10.1017/s0960258500003202.
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AbstractMany research questions focused upon seed dormancy and germination remain unanswered due to problems created by inappropriate assumptions concerning the design and implementation of experiments. Lack of attention to the genetic background and growing conditions required for seed production and subsequent storage may compromise an investigator's ability to pool data or assimilate data trends due to variability in seed performance from year to year. Seed aging events during the afterripening process can be mistaken for those involved in the transition from the dormant to nondormant state. After imbibition, inaccurate criteria for and scoring of the germination event may lead to confusion of seed vs. seedling physiology and biochemistry. In addition, a sufficient number and proper spacing of data points during timecourse experiments are required to properly stage a sequence of events. Studies comparing dormant vs. nondormant seeds must be supplemented with kinetic experiments examining the effect of a dormancy-breaking treatment upon the transition between the dormant and nondormant states. In comparisons of the relative efficacy of various dormancy-breaking chemical treatments, the physical properties of substances under evaluation (e.g. lipophilicity) should be considered. In addition, since many dormancy-breaking chemicals are toxic to vegetative growth, there is a danger of introducing pharmacological artifacts that confuse interpretation of the results obtained. These toxic properties also necessitate the use of viability tests during construction of dose-response curves to avoid confusing seed death with dormancy. Seed scientists must also avail themselves of the extensive literature on developmental arrest in other organisms, which may generate fresh ideas for experimentation.
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Dunbabin, Matthew T., and P. S. Cocks. "Ecotypic variation for seed dormancy contributes to the success of capeweed (Arctotheca calendula) in Western Australia." Australian Journal of Agricultural Research 50, no. 8 (1999): 1451. http://dx.doi.org/10.1071/ar99001.
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The seed dormancy characteristics of 2 capeweed [Arctotheca calendula (L.) Levyns] ecotypes from Western Australia were studied to determine aspects of seed dormancy that contribute to the success of this species in southern Australia. Short- and long-term dormancy pattern of buried and soil surface seed, effect of summer temperatures on afterripening, and effect of temperature on seed germination were investigated using seed produced in a common environment. There were large differences in the seed dormancy pattern of the 2 ecotypes studied. On the soil surface, >95% of seed of the Mt Barker ecotype became non-dormant and germinated in the first year, the remainder germinating the following season. In contrast, only 5% of Mullewa seed germinated in the first year, with 75% germinating in the second year and 20% of seed remaining dormant after 2 years. Cycling of dormancy was observed for buried seed of both ecotypes, with periods of non-dormancy corresponding with the likely timing of the break of the season. Dormancy cycling was also apparent in seed stored under constant conditions in the laboratory. Burial prevented germination of both ecotypes; however, the ability to resist germination while buried was lost in 30% of the Mt Barker seed in the second season. Differences in the duration of dormancy of soil surface and buried capeweed seed have evolved as an adaptation to the different environments likely to be experienced by plants at their site of collection. All seeds possessed primary dormancy at maturity, with any afterripening during the first year occurring by the end of summer. Afterripening was enhanced by exposure to typical soil surface temperatures, providing some protection against germination during early summer rainfall. Protection from late summer rains is insured by the inability of seed to germinate at temperatures >30°C and a relatively slow rate of germination. These features of capeweed seed dormancy, combined with the ability to evolve genetically distinct populations suited to particular environments, help explain why capeweed is so widespread and abundant across southern Australia.
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NOLAN, DARYL G., and MAHESH K. UPADHYAYA. "PRIMARY SEED DORMANCY IN DIFFUSE AND SPOTTED KNAPWEED." Canadian Journal of Plant Science 68, no. 3 (July 1, 1988): 775–83. http://dx.doi.org/10.4141/cjps88-090.
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Large numbers of viable, diffuse (Centaurea diffusa Lam.) and spotted knapweed (C. maculosa Lam.) seeds (achenes), collected in the interior of British Columbia, failed to germinate in darkness at 25 °C. This primary dormancy was released to varying degrees by gibberellic acid, exposure to red light, or excision of the distal end of the seed. The effect of red light was negated by subsequent exposure to far-red light. The demonstration of red/far-red reversibility implicates the phytochrome pigment system in the light-sensitive germination of knapweed seeds. Seeds collected from different sites, and from individual plants within sites, had different germination levels in darkness and following exposure to 2 min of red light. Three types of germination behavior were evident: nondormant seeds germinated in darkness; light-sensitive dormant seeds germinated in response to red light; and light-insensitive dormant seeds failed to germinate after 5 d of continuous red light. Seeds of all three germination types were found on individual plants.Key words: Centaurea diffusa, Centaurea maculosa, knapweed, seed dormancy, light-sensitive germination, germination polymorphism
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Andreoli, Claudinei, Manoel Carlos Bassoi, and Dionisio Brunetta. "Genetic control of seed dormancy and pre-harvest sprouting in wheat." Scientia Agricola 63, no. 6 (December 2006): 564–66. http://dx.doi.org/10.1590/s0103-90162006000600009.
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Pre-harvest sprouting (PHS) damage leads to occasional massive losses in all wheat producing areas, causing downgrading of grain quality, that severely limits end-use applications and results in substantial financial losses to farmers and food processors. Red grain color is a traditional marker for resistance to sprouting in wheat breeding programs, however red-grained genotype alone does not always guarantee effective resistance. The objective of this work was to find genes for resistance to PHS and investigate its inheritance in Brazilian wheat cultivars. Genetic variation for dormancy was investigated in the parents, F1 and 300 F2 lines derived from the cross Frontana × OR1 and its reciprocal. The germination/dormancy sprouted grains was evaluated on fifty seeds per replication, germinated in paper towel rolls at 20ºC for 5 days. A bimodal distribution for dormancy occurred in the Frontana/OR1 and OR1/Frontana derived F2 populations. The mean ratio of dormant and non-dormant seeds of the cross and its reciprocal was 85:1115, fitting a digenic model of 1:15 (P < 0.05). In fact, all non after-ripened F1 seeds germinated. The F2 distribution indicates that two major genes, here called A,a and B,b, control seed dormancy, which it appears to be recessive to dormancy. Only the homozygous aabb is dormant. As expected, there was no effect of maternal tissues.
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Stawska, Marlena, and Krystyna Oracz. "phyB and HY5 are Involved in the Blue Light-Mediated Alleviation of Dormancy of Arabidopsis Seeds Possibly via the Modulation of Expression of Genes Related to Light, GA, and ABA." International Journal of Molecular Sciences 20, no. 23 (November 23, 2019): 5882. http://dx.doi.org/10.3390/ijms20235882.
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Light is one of the most important environmental factors regulating seed germination. It is known that light inhibits seed germination of some monocotyledonous species and that it is mostly related to the blue wavelength of the spectrum received by cryptochromes (cry). Research has also found that the red light (R) stimulates germination of dicotyledonous seeds and that this reaction involves mainly phytochromes (phy). Surprisingly, up to date, the role and the mechanism of action of blue light (BL) in seed biology of dicot plants is still very poorly understood and some questions are unexplained, e.g., whether BL plays a role in regulation of dicot seeds dormancy and/or germination? If, so what particular elements of light signaling pathway are involved in modulation of this(ese) process(es)? Also, is the BL action in regulation of dicot seeds dormancy and/or germination maybe due to changes of expression of genes related to metabolism and/or signaling of two phytohormones controlling seed-related events, such as gibberellins (GA) and abscisic acid (ABA)? To answer these intriguing questions, the combination of biological, transcriptomic, and genetic approaches was performed in this particular study. The germination tests show that freshly harvested wild type (WT) Arabidopsis thaliana Col-0 seeds are dormant and do not germinate in darkness (at 25 °C), while nondormant (after-ripened) seeds germinate well in these conditions. It is also proven that dormancy of seeds of this species is released in the presence of white and/or BL (λ = 447 nm) when placed at 25 °C. Presented here, novel results emphasize the role of BL in dormancy alleviation of dicot seeds, indicating that this wavelength of light spectrum received by phyB induces this process and that the sensitivity to this stimulus depends on the depth of seed dormancy. In addition, it is demonstrated that various elements of phy-mediated pathway can be used in response to the signal induced by BL in germinating dormant seeds of Arabidopsis. The quantitative real time PCR analysis supported by results of germination tests of WT, T-DNA insertion mutants (i.e., hy5, hfr1, and laf1) and overexpression transformants of Arabidopsis seeds (i.e., 35S:OE:HY5, 35S:OE:HYH, 35S:OE:HFR1, and 35S:OE:LAF1) revealed that the HY5 gene coding transcription factor is most probably responsible for the control of expression of genes involved in GA/ABA metabolism and/or signaling pathways during BL-dependent dormancy alleviation of Arabidopsis seeds, while biological functions of HYH and HFR1 are associated with regulation of germination. The model of BL action in regulation of dormancy alleviation and germination potential of Arabidopsis seeds is proposed.
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Chaharsoghi, Ali Tadayyon, and Brent Jacobs. "Manipulating dormancy of capeweed (Arctotheca calendulaL.) seed." Seed Science Research 8, no. 2 (June 1998): 139–46. http://dx.doi.org/10.1017/s0960258500004037.
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AbstractCapeweed (Arctotheca calendula) seeds were found to be dormant at harvest. Effects of duration and temperature of storage under ‘laboratory’ and ‘natural’ conditions, growth regulators, stratification and age of seeds, were studied on the germination of dormant seeds. Three factors imposed on seeds were found to promote germination of capeweed: (i) allowing seed to age, either in storage, buried in soil or during stratification (germination of 18-month-old seeds was up to 60% higher than that of fresh seeds); (ii) the presence of light (the average germination percentage of seeds exposed to light during storage was 3.2-fold greater than that of seed stored in the dark); and (iii) the application of growth regulators, particularly gibberellic acid, enhanced by scarification (GA3and ethephon promoted germination by up to 58% when applied to scarified seeds). Other factors, e.g. temperature and depth of storage, influenced germination but were less critical to its success. These results provide a preliminary assessment of the importance of these factors in controlling dormancy in seeds of capeweed.
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Varis, E., U. Peltola, and R. Kauppila. "Seed yield and seed quality of subterranean clover (Trifolium subterraneum L.) in growing conditions of Finland." Agricultural and Food Science 62, no. 3 (July 1, 1990): 221–26. http://dx.doi.org/10.23986/afsci.72928.
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Seed yield and overwintering of seeds of 22 Australian subterranean clover varieties were investigated in 1986 and 1987 at the Viikki Experimental Farm of the University of Helsinki. The seed yield varied remarkbly according to the variety and weather conditions of the two summers. Some varieties, such as Seaton Park, Woogenellup and Karridale, and during the summer of 1987 also the early variety Dalkeith, produced lots of seed. Some late varieties, e.g. Treeton, Tallarook and Esperance, produced very few seeds or no seeds at all. A considerable proportion of the seeds degenerated during the wet autumn conditions, by the end of October. Many seeds showed embryo dormancy, but complete dormancy or hard seeds were found only exeptionally. In spring 1988, some seedlings which had developed from overwintered burrs were found. There seems to be little hope of finding self-seeding subterranean clovers suitable for Finnish growing conditions.
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Fan, Shugao, Carol C. Baskin, Jerry M. Baskin, and Yanrong Wang. "The seed ecology of Agriophyllum squarrosum, a pioneer sand dune annual in Central Asia, with particular reference to seed germination." Seed Science Research 27, no. 3 (July 19, 2017): 165–73. http://dx.doi.org/10.1017/s0960258517000162.
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AbstractIn central Asia, Agriophyllum squarrosum is the first species to become established during natural succession on sand dunes. However, low germination percentages and thus poor stand establishment greatly inhibit the use of this key species in the stabilization of dunes. The aim of this review is to critically analyse published information on the seed biology of A. squarrosum with particular reference to identifying the factors limiting germination of seeds sown in the field. A conceptual model is used to illustrate the complexities of factors as well as the unknowns we found about the seed/seedling stage of the life cycle of this sand dune annual. A major result of this review is that we now know that high germination percentages can be obtained by storing freshly collected seeds dry at room temperatures for 2 to 3 months to allow dormancy break to occur via afterripening, and then storing them dry at low (e.g. 4–5°C) temperature to prevent them from entering secondary dormancy. Non-dormant seeds should be sown in the field in late spring when wind-blown sand will cover them, thus ensuring that they are in darkness, which promotes germination, at the time summer rains occur.
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Chen, Hua, and M. A. Maun. "Population ecology of Cirsium pitcheri on Lake Huron sand dunes. III. Mechanisms of seed dormancy." Canadian Journal of Botany 76, no. 4 (April 1, 1998): 575–86. http://dx.doi.org/10.1139/b98-029.
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Growth chamber studies were conducted to examine seed dormancy and germination requirements of Pitcher's thistle (Cirsium pitcheri (Torr. ex Eaton) Torr. & Gray), a threatened species endemic to the shoreline sand dunes of the Great Lakes. We determined the effects of different environmental regimes on breaking seed dormancy of this monocarpic perennial. The data showed that seeds of C. pitcheri possessed innate dormancy that was caused by a hard seed coat as well as inhibitory compounds within the seed. Seed germination requirements were very specific. Exposure of seeds to different temperatures and photoperiods in a growth chamber had little effect on breaking seed dormancy unless the seeds had been pretreated. Pretreatment of seeds by cold stratification and its duration, scarification by sand paper or sulphuric acid, and application of gibberellic acid were also not very effective for breaking dormancy of C. pitcheri. High germination was obtained only when seeds were pretreated either by surgically removing the seed coat or by nicking the seed on the radicle or cotyledonary end. After this pretreatment seeds germinated over a temperature range of 15-30°C, but the highest proportion of seeds germinated when temperatures were above 20°C. Under natural conditions, germination of C. pitcheri seeds occurs in spring after they have overwintered and experienced the pretreatment of stratification and scarification through freezing and thawing of the substrate. Aqueous extract of C. pitcheri seeds had a strong inhibitory effect on germination of Oenothera biennis L. seeds indicating an allelopathic chemical in the seed. There was no relationship between the seed size of C. pitcheri and the germinability of seeds.Key words: Cirsium pitcheri, threatened species, seed dormancy, seed germination, scarification, stratification, nicking of seeds.
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Erickson, Todd E., Miriam Muñoz-Rojas, Olga A. Kildisheva, Brad A. Stokes, Stephen A. White, Joanne L. Heyes, Emma L. Dalziell, et al. "Benefits of adopting seed-based technologies for rehabilitation in the mining sector: a Pilbara perspective." Australian Journal of Botany 65, no. 8 (2017): 646. http://dx.doi.org/10.1071/bt17154.
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The use of native plant seeds is fundamental to large-scale rehabilitation and the re-establishment of self-sustaining ecosystems after high-impact mining activity has ceased. However, many of the biological attributes of seeds are often overlooked in large-scale rehabilitation programs. Multi-disciplinary, long-term research collaborations are required to improve seed-based mine rehabilitation. In this paper, we review the steps that BHP Western Australia Iron Ore (WAIO), a large iron ore mining company that operates in the Pilbara bioregion of north-west Western Australia, has taken over the past 9 years to ensure continuous improvement in rehabilitation procedures. We introduce the mining activities that WAIO undertake in the Pilbara, and emphasise specific examples of how research findings have led to incremental improvements in the seed management cycle, growth media management and mine rehabilitation practices. Specifically, we outline how the implementation of structured seed collection and storage programs has created the capacity to maintain high-quality seed stocks sufficient for 3–5 years of future rehabilitation. Research has documented the prevalence of seed dormancy in the flora (>70% of 105 species examined produce dormant seeds), with physical and physiological classes of dormancy most commonly encountered. We discuss the development of seed-treatments such as optimised wet-heat and dry after-ripening that have increased the germination capacity of many previously dormant seed batches. In addition, we highlight how seed enhancement technologies, such as hydro-priming with smoke-derived germination stimulants and polymer seed coating, and a greater understanding of the biological and physical limitations present in the growing environment, have vastly improved seedling emergence performance under field conditions for key framework Triodia species. Ongoing industry support (e.g. construction of a purpose-built rain manipulation shelter) has ensured research in the Pilbara will continue to unpack and resolve the complex challenges associated with seed regeneration of biodiverse native plant communities after mining.
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Dalling, J. W., M. D. Swaine, and Nancy C. Garwood. "Soil seed bank community dynamics in seasonally moist lowland tropical forest, Panama." Journal of Tropical Ecology 13, no. 5 (September 1997): 659–80. http://dx.doi.org/10.1017/s0266467400010853.
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ABSTRACTSeasonal changes in the densities of dormant seeds in the soil around eight pioneer trees in the 50-ha Forest Dynamics Plot, on Barro Colorado Island, Panamá were studied, and how seed dispersal and seed dormancy influenced patterns of seed abundance and distribution were examined. Twenty-four, 3-cm-deep soil samples were collected on 30 m transects radiating out from each of the trees in each of four time-intervals through the year, and four 21-cm-deep samples were collected beneath the focal tree crowns. In the surface 0–3 cm of soil, germinable seed densities of all species combined declined from a peak of 1090 seeds m−2 in the mid-wet season in August, to 330 seeds m−2 by the end of the wet season in November. In contrast, at soil depths >3 cm, there was little variation in soil seed bank density through the year. Some variation in soil seed bank density for individual species could be accounted for by distance to reproductive conspecifics. Among species, abundance in the soil was negatively correlated with seed size. Seed persistence varied greatly among species at this site; after 1 y of burial in mesh bags, seed germinability of four species was near zero, while four other species showed no consistent decline in seed germinability after >2 y of burial. For at least one species, Trema micrantha, prolonged seed dormancy was also possible under natural conditions. Twenty-five percent of Trema seeds extracted from the soil at a site occupied by an isolated Trema tree that died between 1982 and 1985 were still germinable in 1994.
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Kucera, Birgit, Marc Alan Cohn, and Gerhard Leubner-Metzger. "Plant hormone interactions during seed dormancy release and germination." Seed Science Research 15, no. 4 (December 2005): 281–307. http://dx.doi.org/10.1079/ssr2005218.
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This review focuses mainly on eudicot seeds, and on the interactions between abscisic acid (ABA), gibberellins (GA), ethylene, brassinosteroids (BR), auxin and cytokinins in regulating the interconnected molecular processes that control dormancy release and germination. Signal transduction pathways, mediated by environmental and hormonal signals, regulate gene expression in seeds. Seed dormancy release and germination of species with coat dormancy is determined by the balance of forces between the growth potential of the embryo and the constraint exerted by the covering layers, e.g. testa and endosperm. Recent progress in the field of seed biology has been greatly aided by molecular approaches utilizing mutant and transgenic seeds ofArabidopsis thalianaand theSolanaceaemodel systems, tomato and tobacco, which are altered in hormone biology. ABA is a positive regulator of dormancy induction and most likely also maintenance, while it is a negative regulator of germination. GA releases dormancy, promotes germination and counteracts ABA effects. Ethylene and BR promote seed germination and also counteract ABA effects. We present an integrated view of the molecular genetics, physiology and biochemistry used to unravel how hormones control seed dormancy release and germination.
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Gianinetti, Alberto, and Marc Alan Cohn. "Seed dormancy in red rice. XIII: Interaction of dry-afterripening and hydration temperature." Seed Science Research 18, no. 3 (September 2008): 151–59. http://dx.doi.org/10.1017/s0960258508037999.
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AbstractWhile red rice (Oryza sativaL.) can remain dormant and viable for many years when fully imbibed, the environmental factors that stimulate germination or induce secondary dormancy in the field have not been characterized. In this study, the interactions between the extent of dry-afterripening and germination temperature have been evaluated as possible factors. Red rice dispersal units (florets) were afterripened for 0–10 weeks at 30°C and incubated in water at 1, 5, 15, 20, 25, 30 and 35°C for 2 weeks; then, all the ungerminated florets were transferred to 30°C for two additional weeks. Germination at the end of each of the two sequential treatments was compared to define both the effect of differing temperatures on germination (first treatment), and the effect of these temperatures on subsequent germination at the optimum temperature (30°C, second treatment). In afterripening red rice, the opening of the temperature window for germination begins at 25–35°C. Fully dormant florets acquired the ability to germinate ≥ 90% at 30°C after 4 weeks of dry-afterripening. However, imbibing florets for 2 weeks at 15°C followed by 2 weeks at 30°C, yielded suboptimal germination and induced a degree of secondary dormancy, dependent upon the extent of previous dry-afterripening. Cold stratification (1°C) had a consistent promotive effect on the subsequent germination, particularly when preceded by 1–2 weeks of dry-afterripening at 30°C. To monitor the effects of germination temperature, median afterripening time was utilized as a relative dormancy index, and changes in this index have been interpreted as an overlapping of germination and the temperature-induced changes in the dormancy status. Field weather data suggested that low-temperature stratification may be a germination trigger in the field, even in southern Louisiana, and this merits further investigation in studies of soil-buried seeds.
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Torres-González, Alba Marina. "Seed dormancy and germination in tree tomato (Solanum betaceum Cav.) and lulo (Solanum quitoense Lam.)." Revista Colombiana de Ciencias Hortícolas 13, no. 3 (September 1, 2019): 336–47. http://dx.doi.org/10.17584/rcch.2019v13i3.10130.
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Tree tomato (Solanum betaceum Cav.) and lulo (Solanum quitoense Lam.) fruits enjoy high consumption and commercialization in Colombia. Seed dormancy has been reported for both species, and their propagation depends on seeds. The optimal germination conditions for these species are not well known. Thus, the temperature regimes for the seed germination were based on the mean, minimum and maximum temperatures of the locations where the crops were grown. Germination tests were carried out in four replicates of 50 seeds each on Petri dishes for both crops. Six temperature conditions and four pre-treatments were evaluated to break the seed dormancy for several seed lots. S. betaceum and S. quitoese exhibited shallow seed dormancy, and less dormancy was detected in the commercialized cultivars, such as S. betaceum cv. Tamarillo and S. quitoense (i.e. common lulo). For both species, the most recently harvested seeds had more germination capacity than the seeds stored for several months at a low seed moisture content (4%) and low storage temperature (20°C). The seed dormancy of S. betaceum and S. quitoense was broken successfully by applying GA3 (2,000 mg L-1) or alternating temperatures (e.g. 25/15°C). However, both treatments at the same time did not provide an additional benefit to promote seed germination. Potassium nitrate (1%) promoted seed germination in the S. betaceum seeds at both constant and alternating temperatures and in the S. quitoense seeds, only when alternating temperatures were applied. The application of GA3 increased the rate of germination more than KNO3 for both species at all temperatures. Using any of these treatments would work well to break seed dormancy in S. betaceum and S. quitoense, and the most convenient option could be selected depending upon budget and other resources.
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Meisert, A. "Physical dormancy in Geraniaceae seeds." Seed Science Research 12, no. 2 (June 2002): 121–28. http://dx.doi.org/10.1079/ssr2002104.
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Seed dormancy was analysed in Geraniaceae, testing 29,103 seeds of 35 species for seed-coat impermeability to water. Seeds of wild and cultivated species from a number of different climatic/ecological zones (northern Germany, the Canary Islands and South Africa) were investigated. Seeds from cultivated plants and natural populations had similar (±2%) percentages of water-impermeable seeds. The percentages of impermeable seeds at maturity were also mostly constant (±2%) for two different years. The species analysed contained from 0 to 100% impermeable seeds at maturity, and could be classified into three quantitative types of physical dormancy: four species with no impermeable seeds (PY0), 10 species with a maximum of 80% impermeable seeds (PY80), and 21 species with more than 80% impermeable seeds (PY100). Species with different life cycles and from very different habitats, e.g. Geranium pratense or Pelargonium capitatum, belonged to the PY100 group. However, all of the succulent shrubs investigated from the genus Pelargonium were PY0 species. Five years of dry storage at 20 ± 5°C decreased physical dormancy in a species-dependent fashion. Erodium cicutarium, for example, had 95% impermeable seeds at maturity; all of them became permeable during the dry storage and began to germinate immediately after placing them on a moist substrate. Physical dormancy of other species, e.g. Pelargonium zonale, Pelargonium vitifolium or Geranium pratense, was not affected by dry storage. Thus, physical dormancy is a diversely differentiated feature in Geraniaceae with regard to both percentages of impermeable seeds at maturity and maintenance of dormancy under particular conditions.
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Leubner-Metzger, Gerhard. "Functions and regulation of β-1,3-glucanases during seed germination, dormancy release and after-ripening." Seed Science Research 13, no. 1 (March 2003): 17–34. http://dx.doi.org/10.1079/ssr2002121.
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Abstractβ-1,3-Glucanase (βGlu) expression in seeds plays important roles in the regulation of seed germination, dormancy and in the defence against seed pathogens. A thick β-1,3-glucan layer is typical for the seed envelope of cucurbitaceous species, confers seed semipermeability and is degraded during germination. In many species with coat-imposed dormancy, the seed envelope confers a physical constraint to radicle emergence. In the solanaceous species, the micropylar endosperm and testa have this function, and endosperm weakening appears to be a prerequisite for germination. Class I βGlu is transcriptionally induced in the micropylar endosperm of tobacco, tomato and other solanaceous seeds just prior to radicle emergence. βGlu induction and germination are tightly linked in response to plant hormones and environmental factors, e.g. they are both promoted by gibberellins and inhibited by abscisic acid (ABA). Sense and antisense transformation of tobacco reveals two sites of βGlu action: after-ripening-mediated release of testa-imposed dormancy and endosperm rupture during germination. The use of an ABA-inducible chimeric sense-transgene resulted in overexpression of class I βGlu in seeds and provided direct evidence that βGlu contributes to endosperm rupture. A model integrating βGlu, seed dormancy, after-ripening and germination is presented, and possible mechanisms for βGlu action are discussed. It is proposed that βGlu not only helps defend seeds against pathogens, but is also a key factor in regulating coat-imposed dormancy and germination of seeds in response to environmental and hormonal cues.
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Urtasun, María Manuela, Eugenia Mabel Giamminola, and Marta Leonor de Viana. "Southern highland papaya (Vasconcellea quercifolia A. St.-Hil.): Do fruit ripening and harvesting time affect seed germination?" Acta Scientiarum. Agronomy 42 (September 20, 2019): e42825. http://dx.doi.org/10.4025/actasciagron.v42i1.42825.
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In this work, we report the effects of the harvesting time, the stages in fruit ripening and the influence of potassium nitrate in V. quercifolia seed germination. In addition, information about the storage period and light requirements is provided. Fruits were harvested at the beginning and at the end of the fruiting season, and they were classified into five ripening categories. Seed germination was evaluated with two factorial experiments: 1) harvesting time, fruit ripening, and pre-germination treatment; 2) storage and light requirements. The response variables were germination percentage, mean germination time, and seedling vigor. Seeds harvested at the beginning of the season appeared to be less dormant and they were not influenced by fruit ripening or pre-germination treatments. By contrast, seeds harvested at the end of the season were influenced by fruit ripening and pre-germination treatments. Light and seed storage had a positive effect on germination. Mean germination time varied from 12 to 40 days, and vigor index was positively influenced by potassium nitrate. V.quercifolia seeds are photoblastic positive at constant temperatures and their dormancy can be influenced by harvest time, fruit ripening and a storage period.
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Gulden, Robert H., Sheila Chiwocha, Suzanne Abrams, Ian McGregor, Allison Kermode, and Steven Shirtliffe. "Response to abscisic acid application and hormone profiles in spring Brassica napus seed in relation to secondary dormancy." Canadian Journal of Botany 82, no. 11 (November 1, 2004): 1618–24. http://dx.doi.org/10.1139/b04-119.
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The plant hormone abscisic acid (ABA) has been implicated in the inception and maintenance of seed dormancy, while gibberellins promote dormancy breakage and germination in some species. We investigated whether osmotic stress induced secondary dormancy in Brassica napus L. is associated with changes in ABA sensitivity and metabolism, as well as changes in gibberellin levels. Seeds of two genotypes, one with low dormancy potential (LDP) and one with high dormancy potential (HDP) for secondary dormancy, were exposed to a dormancy-inducing osmotic treatment for up to 4 weeks and then germinated in the presence of increasing ABA concentrations. Even at relatively high concentrations of supplied ABA, germination of LDP seed was not inhibited, while relatively low ABA concentrations inhibited the germination of HDP seed after osmotic treatment. Fluridone was highly effective in suppressing secondary dormancy development in HDP seed, but had no effect on germinability in LDP seed. Despite the lack of differences in nonosmotically treated seed, ABA and ABA-glucose ester accumulated to higher levels, and gibberellin A1 accumulated to lower levels, in HDP relative to LDP seed by the end of the osmotic treatment. Our findings indicate an association among ABA sensitivity, biosynthesis and accumulation, and secondary dormancy potential in B. napus seed.Key words: abscisic acid (ABA), Brassica napus, fluridone, induced dormancy, osmotic stress, sensitivity.
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McGinty, Emma M., Kevin M. Murphy, and Amber L. Hauvermale. "Seed Dormancy and Preharvest Sprouting in Quinoa (Chenopodium quinoa Willd)." Plants 10, no. 3 (February 28, 2021): 458. http://dx.doi.org/10.3390/plants10030458.
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Quinoa (Chenopodium quinoa Willd.) is a culturally significant staple food source that has been grown for thousands of years in South America. Due to its natural drought and salinity tolerance, quinoa has emerged as an agronomically important crop for production in marginal soils, in highly variable climates, and as part of diverse crop rotations. Primary areas of quinoa research have focused on improving resistance to abiotic stresses and disease, improving yields, and increasing nutrition. However, an evolving issue impacting quinoa seed end-use quality is preharvest sprouting (PHS), which is when seeds with little to no dormancy experience a rain event prior to harvest and sprout on the panicle. Far less is understood about the mechanisms that regulate quinoa seed dormancy and seed viability. This review will cover topics including seed dormancy, orthodox and unorthodox dormancy programs, desiccation sensitivity, environmental and hormonal mechanisms that regulate seed dormancy, and breeding and non-breeding strategies for enhancing resistance to PHS in quinoa.
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Wang, Xu, Zhazira Yesbergenova-Cuny, Catherine Biniek, Christophe Bailly, Hayat El-Maarouf-Bouteau, and Françoise Corbineau. "Revisiting the Role of Ethylene and N-End Rule Pathway on Chilling-Induced Dormancy Release in Arabidopsis Seeds." International Journal of Molecular Sciences 19, no. 11 (November 13, 2018): 3577. http://dx.doi.org/10.3390/ijms19113577.
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Dormant Arabidopsis (Arabidopsis thaliana) seeds do not germinate easily at temperatures higher than 10–15 °C. Using mutants affected in ethylene signaling (etr1, ein2 and ein4) and in the N-end-rule pathway of the proteolysis (prt6 and ate1-ate2) we have investigated the effects of cold and ethylene on dormancy alleviation. Ethylene (10–100 ppm) and 2–4 days chilling (4 °C) strongly stimulate the germination of wild type (Col-0) seeds at 25 °C. Two to four days of chilling promote the germination at 25 °C of all the mutants suggesting that release of dormancy by cold did not require ethylene and did not require the N-end-rule pathway. One mutant (etr1) that did not respond to ethylene did not respond to GA3 either. Mutants affected in the N-end rule (prt6 and ate1-ate2) did not respond to ethylene indicating that also this pathway is required for dormancy alleviation by ethylene; they germinated after chilling and in the presence of GA3. Cold can activate the ethylene signaling pathway since it induced an accumulation of ETR1, EINI4, and EIN2 transcripts, the expression of which was not affected by ethylene and GA3. Both cold followed by 10 h at 25 °C and ethylene downregulated the expression of PRT6, ATE1, ATE2, and of ABI5 involved in ABA signaling as compared to dormant seeds incubated at 25 °C. In opposite, the expression of RGA, GAI, and RGL2 encoding three DELLAs was induced at 4 °C but downregulated in the presence of ethylene.
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Teketay, Demel, and Anders Granström. "Seed viability of Afromontane tree species in forest soils." Journal of Tropical Ecology 13, no. 1 (January 1997): 81–95. http://dx.doi.org/10.1017/s0266467400010270.
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ABSTRACTThe fate of seeds of eight tree species was followed during 4 y of storage in the soil of an Afromontane forest at Gara Ades in the eastern highlands of Ethiopia. Seeds were enclosed in nylon mesh bags and buried at 5 cm soil depth. The bags were exhumed at intervals and the viability of the seeds was assessed by germination and cutting tests. Seeds of Bersama abyssinica and Ekebergia capensis germinated in the soil almost completely within a year after burial. The seeds of Juniperus procera, Olea europaea and Podocarpus falcatus also germinated to a substantial degree in the soil but with a distribution over several years, and some seeds of these species remained viable at the end of the 4-y period. Germination in the soil was very low in seeds of Acacia abyssinica and Croton macrostachyus throughout the whole burial period and the seeds kept their viability. In C. macrostachyus fresh seeds were highly dormant, but after 3 y or more in the soil they germinated readily in the laboratory suggesting an altered dormancy with time in the soil. Dormancy in seeds of A. abyssinica and Indigofera rothii was not altered throughout the study period as evidenced by marginal or no germination during incubation in the laboratory. The differential seed behaviour observed during storage in the soil can be an indicator of the regeneration strategy of the species studied. B. abyssinica, E. capensis, J. procera, O. europaea and P. falcatus form seedling banks on the forest floor and lack persistent soil seed reserves in contrast to A. abyssinica, C. macrostachyus and I. rothii which accumulate reserves of long-lived seeds in the soil. The generally high levels of dormancy and somewhat extended viability in the soil, even in several of the species producing seedlings in undisturbed forest, may have been selected for under a climate of seasonal drought and unreliable rainfall that characterizes this region.
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Hawkins, K. K., P. S. Allen, and S. E. Meyer. "Secondary dormancy induction and release inBromus tectorumseeds: the role of temperature, water potential and hydrothermal time." Seed Science Research 27, no. 1 (January 10, 2017): 12–25. http://dx.doi.org/10.1017/s0960258516000258.
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AbstractSeeds of the winter annualBromus tectorumlose primary dormancy in summer and are poised to germinate rapidly in the autumn. If rainfall is inadequate, seeds remain ungerminated and may enter secondary dormancy under winter conditions. We quantified conditions under which seeds enter secondary dormancy in the laboratory and field and also examined whether contrastingB. tectorumgenotypes responded differently to dormancy induction cues. The study also extends previous hydrothermal time models for primary dormancy loss and germination timing inB. tectorumby using similar models to account for induction and loss of secondary dormancy. Maximum secondary dormancy was achieved in the laboratory after 4 weeks at –1.0 MPa and 5°C. Seeds in the field became increasingly dormant through exposure to temperatures and water potentials in this range, confirming laboratory results. They were released from dormancy through secondary after-ripening the following summer. Different genotypes showed contrasting responses to dormancy induction cues in both laboratory and field. To examine secondary dormancy induction and release in the field in terms of hydrothermal time parameters, we first created a model that allowed mean base water potential (Ψb(50)) to vary while holding other hydrothermal time parameters constant, as in models for primary dormancy loss under dry conditions. The second model allowed all three model parameters to vary through time, to account for changes (e.g. hydrothermal time accumulation) that could occur simultaneously with dormancy induction in imbibed seeds. Shifts in Ψb(50) could explain most changes in dormancy status for seeds retrieved from the field, except during the short period prior to dormancy induction, when hydrothermal time was accumulating. This study illustrates that hydrothermal modelling, and specifically changes in Ψb(50), can be used to characterize secondary dormancy induction and loss inB. tectorum.
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Renzi, Juan P., Guillermo R. Chantre, and Miguel A. Cantamutto. "Development of a thermal-time model for combinational dormancy release of hairy vetch (Vicia villosa ssp. villosa)." Crop and Pasture Science 65, no. 5 (2014): 470. http://dx.doi.org/10.1071/cp13430.
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Seed dormancy could be a factor related to natural reseeding of hairy vetch (Vicia villosa ssp. villosa Roth.), a winter annual species cultivated for seed, pasture, hay, green manure and cover crop. The presence of combinational dormancy (physical dormancy + physiological dormancy, PY + PD) in hairy vetch was explored by a model using laboratory and field measures. At the stage of natural dispersal, dry seeds of hairy vetch were stored under laboratory conditions at 5, 10, 20 and 30°C (±2°C) or buried at 5 cm depth in an experimental field. Germination at 5, 8, 10, 15, 20 and 25°C was assessed at regular intervals up to 295 days after harvest. Following the hypothesis of the existence of a combinational dormancy mechanism, model development was based on the estimation of: (i) the fraction of non-PY seed as a function of after-ripening thermal-time accumulation, and (ii) seed population thermal parameters associated with a given level of PD. The developed model adequately described the after-ripening thermal-time requirements for PY + PD release of V. villosa. Based on model predictions, under a semi-arid thermal regime, >45% of vetch seeds shed during the summer season would be able to germinate during early autumn. Thus, the seed-bank size threshold at the end of the first growing season should be >65 seeds m–2 in order to reach a minimum stand of 30 plants m–2 necessary for a productive pasture.
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Hatterman-Valenti, Harlene, Iliya A. Bello, and Micheal D. K. Owen. "Physiological Basis of Seed Dormancy in Woolly Cupgrass (Eriochloa villosa[Thunb.] Kunth.)." Weed Science 44, no. 1 (March 1996): 87–90. http://dx.doi.org/10.1017/s0043174500093590.
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Laboratory studies were conducted to determine the effect of seed coat on woolly cupgrass seed moisture and oxygen uptake, and to determine if water-soluble growth inhibitors are present in the seed. Intact dormant seeds did not respond to any temperature regime or to oxygen concentrations above atmospheric level. Dehulling increased germination of dormant seed to about 85%. Oxygen concentrations above atmospheric level increased germination of partially dehulled (1/4 distal end of the seed dehulled) seeds an additional 10%. Oxygen uptake by dehulled dormant and intact nondormant seeds was greater than intact dormant seeds. Leaching intact dormant seeds did not promote germination, nor did the leachate inhibit germination of nondormant seeds. Embryos excised from dormant seeds germinated under laboratory conditions. Results from this study suggest that the woolly cupgrass seed coat may inhibit germination by controlling oxygen availability to the embryo.
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Jianping, Ding. "Introduction and Cultivation of Money Plant (Lunana annus) in Shandong, The People's Republic of China." HortScience 31, no. 4 (August 1996): 656c—656. http://dx.doi.org/10.21273/hortsci.31.4.656c.
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Money plant may be a valuable plant to cultivate as an ornamental plant in China. Money plants are grown for the translucent, silvery, rotund, pseudo-septa that stay on flower stalks and are all that remain of ripened seed pods after the two outer coverings drop with the seeds. Money plant was first introduced from Canada into China in 1993. Seed germination and seedling development were successful. There were 18 to 34 leaves per plant and average plant height was 30 cm by the end of Nov. 1993. Plants exposed to environmental conditions (ENV) became dormant at low temperature. Plants grown under greenhouse conditions (GH) continued to grow until May. ENV plants escaped dormancy between April and May, grew normally, blossomed, and bore pods with seeds. GH plants blossomed; however, most of the blossoms dropped off and seed pods failed to develop. Flower stalks with many lateral inflorescences grew from ENV plant shoot apexes. In some cases, secondary and tertiary branches developed into the secondary and tertiary lateral inflorescences. There were ≈30 flowers per inflorescence and 30% of flowers were developed successfully into pods that usually contained five to six seeds with a maximum of nine seeds per pod. These results indicate that money plant may be successfully cultivated in Shandong, China.
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Puglia, Giuseppe, Simona Grimaldi, Angelino Carta, Pietro Pavone, and Peter Toorop. "Pericarp structure of Glebionis coronaria (L.) Cass. ex Spach (Asteraceae) cypselae controls water uptake during germination." Seed Science Research 25, no. 3 (April 14, 2015): 255–66. http://dx.doi.org/10.1017/s0960258515000148.
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AbstractGlebionis coronaria (L.) Cass. ex Spach is a common Mediterranean weed producing distinctive central and peripheral dormant cypselae with a hard fruit coat, which was previously hypothesized to impose physical dormancy. Analysis of water uptake in cypselae and in naked seeds showed that it preferentially takes place at the basal end of the fruit; however, seeds within an intact pericarp do not fully imbibe when compared with naked seeds. Germination was not significantly different between the two heteromorphs, and afterripening or cold stratification did not increase germination, while warm stratification at 35/20°C, as revealed by logistic regression, resulted in a significant improvement. However, loss of viability was also rapid at these high temperatures. Central and peripheral cypselae generally showed very low germination. In both heteromorphs, faster and higher germination (60–70%) was reached only after extensive scarification of pericarp tissue, and full germination was observed only after complete removal of pericarp tissue. Although the pericarp significantly reduced water uptake, no palisade layer(s) of macrosclereids could be observed. Xylem-vessel elements were found running through the basal end of the pericarp and forming the main point of water entry. We reject the hypothesis that G. coronaria cypselae have physical dormancy. Instead, water uptake and germination are impeded by: (1) directed water uptake, mainly through a pericarp-spanning channel-like structure; and (2) mechanical constraint on embryo growth exerted by the hard pericarp. The channel-like structure forms the principal system for controlling seed germination.
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Bhatt, Arvind, María Mercedes Carón, David Gallacher, and Paulo Roberto de Moura Souza-Filho. "Storage duration, light, temperature, and salinity exposure influence germination of the glycophyte Rhanterium epapposum." Botany 99, no. 5 (May 2021): 261–67. http://dx.doi.org/10.1139/cjb-2020-0153.
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Regeneration of native species is the first priority for biodiversity conservation and restoration. To this end, it is key to have seeds properly conserved in seed banks and knowledge of seed longevity and (or) dormancy alleviation at different storage time intervals. In addition, understanding the germination response of the stored seeds to environmental conditions improves the efficiency of restoration and rehabilitation projects. We investigated the influence of storage duration (1–5 years), light (0 or 12 h of illumination), thermoperiod (night/day temperatures of 15/20 and 20/25 °C), and salinity (0, 100, 200. and 400 mmol/L of NaCl) on seed germination of Rhanterium epapposum, a glycophytic species from the Arabian Peninsula. Seeds maintained viability after five years of storage indoors at room temperature. Three years of storage alleviated seed dormancy. Exposure to 12 h light per day and thermoperiods of 15/20 °C enhanced seed germination. The seeds were glycophytic; after-ripened seeds exposed to salinity exhibited reduced rates of germination that did not recover after the salinity was alleviated.
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Cruz, Eniel David, Rafaela Josemara Barbosa Queiroz, and Jose Edmar Urano de Carvalho. "Methods for overcoming dormancy in Dinizia excelsa Ducke seeds." Revista Brasileira de Sementes 31, no. 4 (2009): 152–59. http://dx.doi.org/10.1590/s0101-31222009000400018.
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The impermeability of seed coat to water is common mechanism in Fabaceae seeds. Treatments to overcome hardseededness include scarification with sulphuric acid, scarification on abrasive surface and soaking in water among others. The objective of this study was to identify an effective method to overcome dormancy in Dinizia excelsa seeds. A pre-test (untreated seed) and three experiments were carried out: immersion of seeds in acid sulphuric for 10, 20, 30, 40, 50 and 60min (experiment 1); scarification on abrasive surface at the positions distal end, near of the mycrophyle and on the lateral tissue and tegument clipping at 1mm of the distal end, near of the mycrophyle and on the lateral tissue (experiment 2); scarification on abrasive surface and immersion in water for 0, 12, 24 and 48h (experiment 3). The experimental design was completely with four replications of 50 seeds for each treatment. The statistical analysis was carried out by ANOVA and regression analysis. Seedlings emergence on untreated seeds started on the 8th day after sowing and reached 52.5% on the 1,709th day. In general, the treatments to overcome dormancy increase emergence. Emergence was higher for seeds treated with sulphuric acid for 20 and 30min with emergence of 93.6% and 86.6%, respectively. For seeds scarified on abrasive surface higher emergences were recorded for scarification on distal end, near of the mycrophyle and on the lateral, 82.7%, 74.3% and 75.7%, respectively. Seeds scarified manually showed higher emergence when not immersed in water (75%), or when immersed for 12 and 24h (75%, 73.6% and 65.6%, respectively). Immersion seeds in sulphuric acid for 20 and 30min and scarification on abrasive surface of distal end are effective to overcome dormancy in D. excelsa.
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Oreja, Fernando H., Diego Batlla, and Elba B. de la Fuente. "Effect of soybean crop structure on large crabgrass (Digitaria sanguinalis) growth and seed dormancy." Weed Science 69, no. 3 (March 2, 2021): 372–78. http://dx.doi.org/10.1017/wsc.2021.17.
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AbstractCrop–weed interactions are affected by environmental alterations resulting from a crop’s presence, such as modifications in temperature, light quality and quantity, and moisture conditions that could modify weed performance. The objectives of this work were to study (1) how soybean [Glycine max (L.) Merr.] crop structure modifies the environment under the canopy and large crabgrass [Digitaria sanguinalis (L.) Scop.] plant structure, biomass, and seed production and dormancy; and (2) the relative importance of these environmental changes on the weed’s characteristics. A field experiment in a completely randomized block design with five replicates was performed to evaluate narrow and wide interrow spacing and soybean maturity groups 3 and 4. Measured variables were intercepted solar radiation (RAD); red–far red (R-FR) ratio; humidity; minimum, maximum, and alternating temperatures; and weed biomass, tillers per plant, height, and seed dormancy. Crop canopy reduced solar radiation, R-FR ratio, and daily average maximum and alternating temperatures. Soybean presence reduced the weed biomass, tillers and seeds per plant, and seed dormancy. High solar radiation intercepted by the crop during the reproductive phase was the main environmental variable related to reductions in weed biomass, tillers per plant, and fecundity. The combination of low temperature and solar radiation received by developing seeds was more related to seed dormancy than the rest of the variables. Crop management decisions focused on the fact that keeping the crop canopy alive for a longer time at the end of the season would not only reduce the weed growth but also seed dormancy.
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Tomaz, Camila de Aquino, Cibele Chalita Martins, Mauricio Feis Ganz Sanches, and Roberval Daiton Vieira. "TIME REDUCTION FOR SURINAM GRASS SEED GERMINATION TEST." Ciência e Agrotecnologia 39, no. 5 (October 2015): 488–97. http://dx.doi.org/10.1590/s1413-70542015000500007.
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ABSTRACTThe period for the germination test of Surinam grass seeds established by the Rules for Seeds Testing is 28 days, considered too lengthy by producers, venders, and seed analysis laboratories. So, the objective of this research was to evaluate the possibility of reducing the time for the germination test of Surinam grass seeds and to establish a method for dormancy breaking and the ideal temperature. Ten seed lots were submitted to the following treatments to overcome seed dormancy: control; substrate moistening with 0.2% KNO3; and scarification with sulfuric acid (98% 36 N) for 15 minutes. After the treatments, the lots were submitted to seed water content, germination and tetrazolium tests. During the germination test, conducted with four replicates of 100 seeds per treatment for 28 days, two conditions of alternating temperatures (20-35 °C and 15-35 °C) with 8 hours of light were tested. Attempting to determine the test end date, daily counts of the number of normal seedlings were made and for each lot, treatment, and temperature, a growth curve for the evaluation of germination was adjusted. The segmented regression model parameter estimations were calculated for each treatment. The germination test of Braquiaria decumbensseeds may be evaluated in 12 days after sowing using alternating temperatures of 20-35 °C and without any treatment to overcome dormancy.
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Briggs, Candida L., E. Charles Morris, and Glenn Stone. "Micropylar seed coat restraint and embryonic response to heat shock and smoke control seed dormancy in Grevillea juniperina." Seed Science Research 26, no. 2 (June 2016): 111–23. http://dx.doi.org/10.1017/s0960258516000088.
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AbstractSeeds of some eastern Australian Grevillea species show the characteristics of non-deep physiological dormancy, which is broken by exposure to heat shock and/or smoke. The current study tested whether the restrictive effect of the seed coat on germination was localized to specific regions, whether the fire cues affected the growth potential of the embryo, the mechanical strength of the seed coat itself, and the anatomy of fracturing of the seed coat. Removal of the micropylar seed coat allowed germination, while retaining it in place restricted germination. The growth potential of the embryo was increased by exposure to heat shock or to smoke, and increased the most if exposed to both cues. Estimation of the minimum force required by embryos to germinate from intact seeds suggested that this force was reduced for seeds treated with fire cues. The fire cues did not affect the resistance of the seed coat to compressive force when tested after 24 h of imbibition. Fracturing of the seed coat occurred between cell walls, except for the palisade layer, where fracturing occurred across palisade and sclerenchyma cells. While the micropylar end of the seed coat imposes dormancy, most likely by mechanical constraint, heat shock and smoke overcome dormancy by increasing the embryo's growth potential and possibly weakening the seed coat, either directly or via the embryo.
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Gomes, Daniele Rodrigues, Maristela Machado Araujo, Ubirajara Rossi Nunes, and Suelen Carpenedo Aimi. "Biometry and germination of Balfourodendron riedelianum Eng. Eng." Journal of Seed Science 38, no. 3 (August 22, 2016): 187–94. http://dx.doi.org/10.1590/2317-1545v38n3159311.
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Abstract This study investigated the biometry, pre-germination treatments and substrates for the germination of diaspores of Balfourodendron riedelianum. The diaspores were characterized during germination according to their length, width, thickness, thousand kernel weight (TKW) and water content. Dormancy overcoming was tested by diaspore scarifying with sandpaper, sulfuric acid immersion, water and water at 100 °C; together with the control (untreated), they were associated to different substrates (including paper (EP), sand (EA) and vermiculite (EV). Germination tests were conducted in a germination chamber at 25 °C. The physiological quality of seeds was performed through the first count, germination and germination speed index (GSI). Biometric data were analyzed in frequency classes and the pre-germination treatment by analysis of variance. Diaspores are on average 18.59 mm long; 9.03 mm wide and 9.38 mm thick. The treatment of immersion in cold water for 48 hours and the substrate vermiculite (EV) were effective to overcome dormancy and recommended for germination tests.
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Gómez-González, Susana, Maria Paniw, Mario Durán, Sergio Picó, Irene Martín-Rodríguez, and Fernando Ojeda. "Mediterranean Heathland as a Key Habitat for Fire Adaptations: Evidence from an Experimental Approach." Forests 11, no. 7 (July 10, 2020): 748. http://dx.doi.org/10.3390/f11070748.
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Some fire ecology studies that have focused on garrigue-like vegetation suggest a weak selective pressure of fire in the Mediterranean Basin compared to other Mediterranean-type regions. However, fire-prone Mediterranean heathland from the western end of the Mediterranean Basin has been frequently ignored in the fire ecology literature despite its high proportion of pyrogenic species. Here, we explore the evolutionary ecology of seed traits in the generalist rockrose Cistus salviifolius L. (Cistaceae) aiming to ascertain the role of the Mediterranean heathland for fire adaptations in the Mediterranean Region. We performed a germination experiment to compare the relationship of seed size to (i) heat-stimulated germination, (ii) dormancy strength, and (iii) heat survival in plants from ‘high-fire’ heathland vs. ‘low-fire’ coastal shrubland. Germination after heat-shock treatment was higher in large seeds of both ‘high-fire’ and ‘low-fire’ habitats. However, dormancy was weaker in small seeds from ‘low-fire’ habitats. Finally, seed survival to heat shock was positively related to seed size. Our results support that seed size is an adaptive trait to fire in C. salviifolius, since larger seeds had stronger dormancy, higher heat-stimulated germination and were more resistant to heat shock. This seed size–fire relationship was tighter in ‘high-fire’ Mediterranean heathland than ‘low-fire’ coastal shrubland, indicating the existence of differential fire pressures and evolutionary trends at the landscape scale. These findings highlight the Mediterranean heathland as a relevant habitat for fire-driven evolution, thus contributing to better understand the role of fire in plant evolution within the Mediterranean region.
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Aragón-Gastélum, José Luis, Joel Flores, Enrique Jurado, Hugo M. Ramírez-Tobías, Erika Robles-Díaz, Juan Pablo Rodas-Ortiz, and Laura Yáñez-Espinosa. "Potential impact of global warming on seed bank, dormancy and germination of three succulent species from the Chihuahuan Desert." Seed Science Research 28, no. 4 (August 7, 2018): 312–18. http://dx.doi.org/10.1017/s0960258518000302.
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AbstractWe assessed inter-seasonal dynamics of seed banks, dormancy and seed germination in three endemic Chihuahuan Desert succulent species, under simulated soil warming conditions. Hexagonal open top-chambers (OTCs) were used to increase soil temperature. Seeds ofEchinocactus platyacanthus(Cactaceae),Yucca filiferaandAgave striata(Asparagaceae) were collected and buried within and outside OTCs. During the course of one year, at the end of each season, seed batches were exhumed to test viability and germination. Soil temperature in OTCs was higher than in control plots.Yucca filiferaseeds always had high germination independently of warming treatment and season.Agave striataseeds from OTCs had higher germination than those from control plots.Agave striataexhibited low germination in fresh seeds, but high germination in spring. Seeds from this species lost viability throughout the experimental timeframe, and had no viable seeds remaining in the soil.Echinocactus platyacanthusshowed high germination in fresh seeds and displayed dormancy cycling, leading to high germination in spring, low germination in summer and autumn, and high germination in winter. Germination of this species was also higher in seeds from OTCs than those from control plots.Echinocactus platyacanthusformed soil seed banks and its cycle of inter-seasonal dormancy/germination could be an efficient physiological mechanism in a climate change scenario. Under global warming projections, our results suggest that future temperatures may still fall within the three studied species’ thermal germination range. However, higher germination forA. striataandE. platyacanthusat warmer temperatures may reduce the number of seeds retained in the seed bank, and this could be interpreted as limiting their ability to spread risk over time. This is the first experimental study projecting an increase in soil temperature to assess population traits of succulent plants under a climate change scenario for American deserts.
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Khan, Anwar A. "Induction of Dormancy in Nondormant Seeds." Journal of the American Society for Horticultural Science 119, no. 3 (May 1994): 408–13. http://dx.doi.org/10.21273/jashs.119.3.408.
Full textAbstract:
A gibberellic acid (GA) biosynthesis inhibitor, tetcyclacis, induced dormancy in nondormant seeds of lettuce (Lactuca sativa L.), tomato (Lycopersicon esculentum Mill.), pepper (Capsicum annuum L.), carrot [Daucus carota var. sativus (Hoffn.)], onion (Allium cepa L.), celery (Apium graveolens L.), and impatiens (Impatiens novette), as most of the seeds failed to germinate after washing under conditions that permitted germination before dormancy induction. In lettuce seeds, tetcyclacis and paclobutrazol were more effective in inhibiting germination in light than in darkness. A 16- to 24-h soak treatment with tetcyclacis was sufficient to induce dormancy in nearly all seeds. Tetcyclacis failed to induce dormancy if applied after 6 h presoak in water. Dormancy induced by tetcyclacis was released by GA4+7 (a mixture of gibberellin A4 and A7), light, and moist-chilling treatments. When GA4+7 was applied with tetcyclacis, dormancy induction was prevented under both favorable, e.g., 25C, and unfavorable, e.g., 5C, or low water potential (Ψ), germination conditions. Unlike tetcyclacis, abscisic acid (ABA) failed to induce dormancy in lettuce seeds. Thermodormancy induction in lettuce seeds at 35C was prevented by fluridone. However, neither ABA nor tetcyclacis countered its effect. Dormancy was also induced in lettuce seeds by ancymidol, flurprimidol, or paclobutrazol. Dormancy induced by tetcyclacis in pepper, tomato, carrot, and onion seeds was released by GA4+7, but not by irradiation or moist-chilling. Chemical names used: 5-(4-chlorophenyl)-3, 4, 5, 9, 10-pentaazatetracyclo [5.4.102,6.08,11]-dodeca-3, 9-diene (tetcyclacis); 1-(4-chlorophenyl)-4, 4-dimethyl-2-(1H-1, 2, 4-triazole-1-yl)-3-pentanol (paclobutrazol); α-cyclopropyl-α-(4-methoxyphenyl)-5-pyrimidine methanol (ancymidol); α-(1-methyl)-α-[4-(trifluoromethoxy) phenyl]-5-pyrimidine-methanol (flurprimidol); 1-methyl-3-phenyl-5-[3-(trifluoromethyl)phenyl]-4 (1H)-pyridinone (fluridone).
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Battaglia, M. "Effects of Seed Dormancy and Emergence Time on the Survival and Early Growth of Eucalyptus delegatensis and E. amygdalina." Australian Journal of Botany 44, no. 2 (1996): 123. http://dx.doi.org/10.1071/bt9960123.
Full textAbstract:
Seed of two tree species, Eucalyptus amygdalina Labill. and E. delegatensis R.T.Baker, was sown on 12 separate dates at two sites close to which both occurred. The species have parapatric distributions but form ecotonal stands. One site was harsh by comparison to the other. Recruitment, survival and growth were recorded at regular intervals following sowing and were related to temperature and soil moisture. The non-dormant seed fraction of both species responded similarly to environmental cues, with rapid emergence occurring when the mean daily temperature exceeded 6°C and the soil moisture index was below 30 mm. Differences in the pattern of emergence between the species resulted from differing degrees of seed dormancy. On the harsh site, spring emergence gave superior survival and growth than did autumn emergence. Consequently, spring emergents were dominant at the end of the experiment. At the milder of the two sites, little difference in survival or growth was observed between emergence times and consequently seedlings emerging in the autumn were dominant at the end of the experiment. Differences between the mortality rate of very young seedlings of each species were detected at some times of year. The combination of differences in seedling mortality, and patterns of emergence as a result of seed dormancy suggest that differences in the regeneration niche may act to reinforce species boundaries, and combined with spatial and temporal variation in regeneration conditions may promote coexistence in ecotonal stands.
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Paynter, BH, and KW Dixon. "Propagation of yellow bells (Geleznowia verrucosa Turcz., Rutaceae) from seed." Australian Journal of Agricultural Research 42, no. 5 (1991): 901. http://dx.doi.org/10.1071/ar9910901.
Full textAbstract:
Geleznowia verrucosa Turcz. (Rutaceae) is a commercially important, bush-picked wildflower that has no known commercial means of propagation. This study examined factors influencing seed dormancy and likely to restrict germination of the species. Germination of entire, untreated seed was low (less than 2%), but removal of a small portion of the testa at or near the radicle end of the seed improved germination. This response was affected by the temperature under which the seed germinated, but was unaffected by exposure of the seed to light while germinating. The percentage germination of nicked seeds 52 days after sowing increased from 8% to 16-19% by increasing the temperature from 15/10�C to 20/15�C; 55-60% of nicked seed germinated when the germination temperature was increased to 23/15�C. The germination of nicked seed was reduced by leaching in running tap water. Following 1 week of leaching the germination percentage of nicked seed at day 52 in the glasshouse was reduced from 16% to 9%, with a further decrease to 5% after 2 weeks of leaching. There was also no stimulatory effect on the germination of entire seeds by stratifying the seed at 5�C after periods of solarisation. It is concluded that dormancy of fresh seeds of G. verrucosa is caused, in part, by the mechanical restriction of the testa on embryo growth and elongation.
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Gómez-González, Susana, Maria Paniw, Kamila Antunes, and Fernando Ojeda. "Heat shock and plant leachates regulate seed germination of the endangered carnivorous plant <i>Drosophyllum lusitanicum</i>." Web Ecology 18, no. 1 (January 29, 2018): 7–13. http://dx.doi.org/10.5194/we-18-7-2018.
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Abstract. In fire-prone ecosystems, many plant species have specialized mechanisms of seed dormancy that ensure a successful recruitment after fire. A well-documented mechanism is the germination stimulated by fire-related cues, such as heat shock and smoke. However, less is known about the role of inhibitory germination signals (e.g. allelopathy) in regulating post-fire recruitment. Plant leachates derived from the unburned vegetation can enforce dormancy by means of allelopathic compounds, acting as a signal of unfavourable (highly competitive) niche for germination in pyrophyte species. Here, we assessed the separate effects of heat shock and plant leachates on seed germination of Drosophyllum lusitanicum, an endangered carnivorous plant endemic to Mediterranean fire-prone heathlands. We performed a germination experiment in which seeds were subjected to three treatments: (1) 5 min at 100 ∘C, (2) watering with plant leachate, and (3) control. Germination rate and seed viability was determined after 63 days. Heat shock stimulated seed germination in D. lusitanicum while plant leachates had inhibitory germination effects without reducing seed viability. Thus, both positive and negative signals could be involved in its successful post-fire recruitment. Fire would break seed dormancy and stimulate seed germination of D. lusitanicum through high temperatures, but also by eliminating allelochemical compounds from the soil. These results help to understand the population dynamics patterns found for D. lusitanicum in natural populations, and highlight the role of fire in the ecology and conservation of this endangered species. Seed dormancy imposed by plant-derived leachates as an adaptive mechanism should be considered more in fire ecology theory.
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Newton, Gina M., and Brad D. Mitchell. "Egg dormancy in the Australian estuarine-endemic copepods Gippslandia estuarina and Sulcanus conflictus, with reference to dormancy of other estuarine fauna." Marine and Freshwater Research 50, no. 5 (1999): 441. http://dx.doi.org/10.1071/mf98161.
Full textAbstract:
The presence of dormant life history stages was investigated for the zooplankton of an annually flooding salt-wedge estuary. Such stages are seen as a potential mechanism for population persistence following environmental adversity. Laboratory incubation experiments were conducted on estuarine sediments. As a result, dormant eggs in Australian estuarine-endemic copepods are reported for the first time. Nauplii of the dominant estuarine-endemic calanoids Gippslandia estuarina and Sulcanus conflictus commonly hatched from the sediments. Manipulation of the salinity and temperature of experimental media indicated that temperature was the more important hatching trigger for S. conflictus, and that both high salinity and high temperature were important for G. estuarina. Results of the incubation experiments, including those of ‘conversion’ experiments (i.e. from freshwater to saline conditions or low temperature to high temperature), help to elucidate the type of dormancy characteristic of each species; it appears that S. conflictus may have diapause eggs and G. estuarina may have quiescent eggs, although this is yet to be confirmed. Other estuarine fauna developed from the mud during the incubation experiments, most notably the harpacticoids Onychocamptus chathamensis, an ectinosomatid and Schizopera sp., and the medusa Australomedusa baylii. Ecological and evolutionary consequences of dormancy in these estuarine-endemic zooplankton are briefly discussed.
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Illescas-Gallegos, Everardo, Dante Arturo Rodríguez-Trejo, Antonio Villanueva-Morales, Amparo Borja-de la Rosa, Víctor R. Ordóñez-Candelaria, and Luis A. Ortega-Aragón. "Factors influencing physical dormancy and its elimination in two legumes." Revista Chapingo Serie Ciencias Forestales y del Ambiente 27, no. 3 (August 31, 2021): 413–29. http://dx.doi.org/10.5154/r.rchscfa.2020.06.041.
Full textAbstract:
Introduction: Prosopis laevigata (Humb. & Bonpl. ex Willd.) M. C. Johnst, P. glandulosa Torr., Vachellia schaffneri (S. Watson) Seigler & Eibinger, V. pennatula (S. Watson) Seigler & Eibinger and V. farnesiana (L.) Wight & Arn. are characteristic species of semi-arid areas. Their seeds show physical dormancy and are naturally scarified by chewing, trampling, digestive tract of fauna, fire, or washing away during rains. Objective: To describe the morphology of the seed coat of three species of Vachellia and two of Prosopis, and to assess the chemical, mechanical and thermal scarification of seeds. Materials and methods: Chemical (HCl for 30, 120, 150 and 180 min), thermal (80, 100, 120 and 140 °C for 3 min) and mechanical (sanding) scarification were applied. Resistance to breaking by compression was measured. The experimental design was randomized complete blocks per species. Results and discussion: Seeds showed a layer of lignified and impermeable macrosclereids, but the aleurone layer could not be detected. Sanding allowed germination from 81.2 to 100 %. Chemical and thermal treatments showed no differences, only in the case of P. laevigata, chemical scarification for 180 min caused higher germination (72.5 %) compared to the control. Vachellia schaffneri seeds were more resistant to compression (669 N) and had more intense dormancy (0.83), while P. glandulosa had the lowest dormancy (0.42). Conclusions: Mechanical scarification was the best method to eliminate dormancy in Vachellia and Prosopis seeds.
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Erickson, Todd E., David J. Merritt, and Shane R. Turner. "Overcoming physical seed dormancy in priority native species for use in arid-zone restoration programs." Australian Journal of Botany 64, no. 5 (2016): 401. http://dx.doi.org/10.1071/bt16059.
Full textAbstract:
The relative effectiveness of wet- and dry-heat treatments on alleviating physical dormancy (PY) of seeds of seven species of Fabaceae and five species of Malvaceae was determined to optimise seed handling procedures for ecological restoration. Seeds of all species were treated at different temperatures (40−100°C) for various durations (2 and 5 min of wet heat, and 5, 10 and 30 min of dry heat). Prior to treatment, seeds of all species exhibited low germination (0–38%). As hypothesised, there was variation among species with respect to the efficacy of the heat treatments. In general, wet-heat treatments at temperatures >70°C for 2 or 5 min were effective in breaking PY for all Fabaceae species, and two Malvaceae species, with resultant germination typically >75%. For dry-heat treatments, higher temperatures and longer durations were required to achieve similar germination results. In the three Malvaceae species that were least responsive to heat (Abutilon otocarpum, Hibiscus haynaldii and Sida echinocarpa), there was a trade-off between treatment temperature and duration; lower temperatures (<70°C) failed to alleviate PY, whereas higher temperatures either rendered seeds permeable but not germinable (70−90°C), or resulted in seeds losing viability (e.g. 100°C). Therefore, combinational dormancy (PY + physiological dormancy) appears to be present in a proportion of the seeds of these Malvaceae species (i.e. those that imbibed and remained viable, but did not germinate). Scanning electron imagery established that the majority of wet-heat treatments resulted in the rupture of the water gap in the seed testa of all species. The results clearly demonstrate that optimal heat treatments for the alleviation of PY are species-specific. Restoration practitioners handling seeds of diverse species should be mindful of treating seeds at the lowest effective temperature (70−90°C) to avoid injury through inadvertent exposure to temperatures that are higher and longer than necessary to break dormancy.
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Bonnardeaux, Y., C. Li, R. Lance, X. Q. Zhang, K. Sivasithamparam, and R. Appels. "Seed dormancy in barley: identifying superior genotypes through incorporating epistatic interactions." Australian Journal of Agricultural Research 59, no. 6 (2008): 517. http://dx.doi.org/10.1071/ar07345.
Full textAbstract:
A genetic linkage map of barley with 128 molecular markers was constructed using a doubled haploid (DH) mapping population derived from a cross between barley (Hordeum vulgare) cvv. Stirling and Harrington. Quantitative trait loci controlling seed dormancy were characterised in the population. A major quantitative trait locus (QTL) controlling seed dormancy and accounting for over half the phenotypic variation (52.17%) was identified on the distal end of the long arm of chromosome 5H. Minor QTLs were also detected near the centromeric region of 5H and on chromosomes 1H and 3H. These minor QTLs with additive effects accounted for 7.52% of the phenotypic variance measured. Examination of epistatic interactions further detected additional minor QTLs near the centromere of 2H and on the long arm and short arms of 4H. Combinations of parental alleles at the QTL locations in predictive analyses indicated dramatic differences in germination. These results emphasise the potential differences in dormancy that can be achieved through the use of specific gene combinations and highlights the importance of minor genes and the epistatic interactions that occur between them. This study found that the combination of Stirling alleles at the two QTL locations on the 5H chromosome and Harrington alleles at the 1H and 3H QTL locations significantly produced the greatest dormancy. Uncovering gene complexes controlling the trait may enable breeders to produce superior genotypes with the desirable allele combinations necessary for manipulating seed dormancy in barley.
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Staszak, Aleksandra M., Monika Rewers, Elwira Sliwinska, Ewelina A. Klupczynska, and Tomasz A. Pawlowski. "DNA synthesis pattern, proteome, and ABA and GA signalling in developing seeds of Norway maple (Acer platanoides)." Functional Plant Biology 46, no. 2 (2019): 152. http://dx.doi.org/10.1071/fp18074.
Full textAbstract:
Mature seeds of Norway maple exhibit desiccation tolerance and deep physiological dormancy. Flow cytometry, proteomics, and immunodetection have been combined to investigate seed development of this species. DNA content analysis revealed that cell cycle/endoreduplication activity differs between seed organs and developmental stages. In the embryo axis, the proportion of the nuclei with the highest DNA content (4C) increases at the beginning of maturation (17 weeks after flowering; WAF), and then is stable until the end of maturation, to increase again after drying. In cotyledons, during maturation endopolyploid nuclei (8C) occur and the intensity of endoreduplication increases up to 21 WAF, and then is stable until development is completed. In dry mature seeds, the proportion of 4C nuclei is high, and reaches 36% in the embryo axis and 52% in cotyledons. Proteomic studies revealed that energy and carbon metabolism, fatty acid biosynthesis, storage and antioxidant proteins are associated with seed development. Study of the ABI5 protein, a transcription factor involved in ABA signalling, and the RGL2 protein, a repressor of the GA signalling indicates that the highest accumulation of these proteins occurs in fully-matured and dried seeds. It is suggested that this increase in accumulation can be associated with completion of maturation, mainly with desiccation and dormancy acquisition.
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Meyer, Susan E., Julie Beckstead, and Phil S. Allen. "Niche specialization in Bromus tectorum seed bank pathogens." Seed Science Research 28, no. 3 (June 13, 2018): 215–21. http://dx.doi.org/10.1017/s0960258518000193.
Full textAbstract:
AbstractNiche theory predicts that when two species exhibit major niche overlap, one will eventually be eliminated through competitive exclusion. Thus, some degree of niche specialization is required to facilitate coexistence. We examined whether two important seed bank pathogens on the invasive winter annual grass Bromus tectorum (cheatgrass, downy brome) exhibit niche specialization. These pathogens utilize seed resources in complementary ways. Pyrenophora semeniperda is specialized to attack dormant seeds. It penetrates directly through the seed coverings. Hyphae ramify first through the endosperm and then throughout the seed. Seed death results as the embryo is consumed. In contrast, the Fusarium seed rot pathogen (Fusarium sp.) is specialized to attack non-dormant seeds in the early stages of germination. It cannot penetrate seed coverings directly. Instead, it responds to a cue emanating from the radicle end with directional hyphal growth and subsequent penetration at the point of radicle emergence, causing seed death. Non-dormant seeds usually escape P. semeniperda through germination even if infected because it develops more slowly than Fusarium. When water stress slows non-dormant seed germination, both P. semeniperda and Fusarium can attack and cause seed mortality more effectively. The Fusarium seed rot pathogen can sometimes reach epidemic levels and may result in B. tectorum stand failure (‘die-off’). Stands usually re-establish from the persistent seed bank, but if P. semeniperda has also reached high levels and eliminated the seed bank, a die-off can persist indefinitely.
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Murray, David, and Razmik Mirzayans. "Cellular Responses to Platinum-Based Anticancer Drugs and UVC: Role of p53 and Implications for Cancer Therapy." International Journal of Molecular Sciences 21, no. 16 (August 11, 2020): 5766. http://dx.doi.org/10.3390/ijms21165766.
Full textAbstract:
Chemotherapy is intended to induce cancer cell death through apoptosis and other avenues. Unfortunately, as discussed in this article, moderate doses of genotoxic drugs such as cisplatin typical of those achieved in the clinic often invoke a cytostatic/dormancy rather than cytotoxic/apoptosis response in solid tumour-derived cell lines. This is commonly manifested by an extended apoptotic threshold, with extensive apoptosis only being seen after very high/supralethal doses of such agents. The dormancy response can be associated with senescence-like features, polyploidy and/or multinucleation, depending in part on the p53 status of the cells. In most solid tumour-derived cells, dormancy represents a long-term survival mechanism, ultimately contributing to disease recurrence. This review highlights the nonlinearity of key aspects of the molecular and cellular responses to bulky DNA lesions in human cells treated with chemotherapeutic drugs (e.g., cisplatin) or ultraviolet light-C (a widely used tool for unraveling details of the DNA damage-response) as a function of the level of genotoxic stress. Such data highlight the growing realization that targeting dormant cancer cells, which frequently emerge following conventional anticancer treatments, may represent a novel strategy to prevent or, at least, significantly suppress cancer recurrence.
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Milberg, Per, and Lars Andersson. "Seasonal variation in dormancy and light sensitivity in buried seeds of eight annual weed species." Canadian Journal of Botany 75, no. 11 (November 1, 1997): 1998–2004. http://dx.doi.org/10.1139/b97-911.
Full textAbstract:
We recorded germination in three different light environments (light, dark, and after a short light exposure) in eight annual weed species. Seeds were buried outdoors at the end of November 1994 and exhumed monthly from March 1995 to April 1996. All species exhibited substantial seasonal changes in dormancy level, and the patterns suggest that seeds of Papaver rhoeas germinate strictly in the autumn; Capsella bursa-pastoris, Descurainia sophia, Spergula arvensis, and Urtica urens mainly in the autumn; Chenopodium suecicum strictly in the spring; and Matricaria perforata mainly in the spring. Lapsana communis showed inconsistent dormancy changes over the year. All species had acquired a light requirement for germination after being in the soil, and in many cases the short light exposure (1050 μmol∙m−2) was enough to fulfil this requirement. The demonstrated seasonal changes in light sensitivity in several of the species will have to be taken into account in attempts to photocontrol weeds. By using the short-light treatment, we were able to detect seasonal dormancy changes that would not have been obvious by testing for germination in only light and darkness. Hence, light is not a simple dichotomous factor in its effect on germination. Key words: dormancy, germination, light, seed, Sweden, weed.
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Bell, Michael S., and Patrick J. Tranel. "Time Requirement from Pollination to Seed Maturity in Waterhemp (Amaranthus tuberculatus)." Weed Science 58, no. 2 (June 2010): 167–73. http://dx.doi.org/10.1614/ws-d-09-00049.1.
Full textAbstract:
Experiments were conducted to determine the amount of time required for waterhemp to produce mature seeds after pollination. Female waterhemp plants were pollinated over a 24-h time period and then isolated from males. Two branches, each containing at least 500 flowers, were harvested from each female at the time of the initial pollination, designated as 0 d after pollination (DAP), as well as at multiple other times after pollination up to 62 DAP. One branch from each harvest was stored at 30 C for 48 h, while the other branch was stored at −20 C for 48 h. Branches were then stored at room temperature until all harvests were complete, at which time seeds from each branch at each time after pollination were collected, weighed, and stratified. Germination tests were then conducted to determine the time at which seeds become viable after pollination. Seeds that had not germinated by the end of the germination tests were subjected to tetrazolium testing for viability. Germination tests were also conducted on nonstratified seeds to investigate changes in seed dormancy that were expected to occur over the amount of time the seeds were allowed to remain on the plants. Seeds stored initially at 30 C postharvest became viable 7 to 9 DAP, whereas seeds stored initially at −20 C postharvest did not become mature until 11 DAP. Seed coat color was white soon after pollination and became dark brown to nearly black by 12 DAP, and seed weight increased until 12 DAP. Tetrazolium tests for seed viability correlated well with the germination tests. Germination tests on nonstratified seeds indicated that dormancy level was initially high in the population used, but began to decrease between 15 and 30 DAP. Results of this study have implications both for waterhemp management and research.