Dissertations / Theses on the topic 'Seed dormancy'
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Xia, Qiong. "Molecular aspects of temperature regulation of sunflower seed dormancy." Thesis, Paris 6, 2016. http://www.theses.fr/2016PA066629/document.
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La graine est le produit de la reproduction sexuée chez les Angiospermes. Elle assure la survie et la dispersion de l'espèce. La germination des graines est la première étape de la croissance des plantes. La transition entre l'état de dormance des graines et leur germination est une étape clef dans le cycle de vie des plantes qui a des conséquences écologique et commerciale. Depuis plusieurs décennies, de nombreux facteurs de l'environnement ont été étudiés pour leurs implications et leurs conséquences dans le processus de dormance et de germination des graines. Les études sur la réponse des semences aux changements de température en liens avec le réchauffement climatique ont un intérêt primordial. Le but de ce travail a été d'étudier la régulation de la dormance et de la germination des graines de tournesol par la température. Une analyse protéomique et un profilage enzymatique ont été réalisés afin de mieux comprendre la régulation du métabolisme pendant la levée de dormance par la température. L'utilisation d'approches moléculaires et cytologiques, nous ont permis d'appréhender l'interaction entre la température et les phytohormones impliquées dans ce processus. Nos résultats ont révélé le rôle joué par la température comme facteur externe affectant la dormance et la germination des graines en agissant d'une part sur le métabolisme et d'autre part sur la quantité et la localisation cellulaire des principales hormones endogènesA seed is the product of sexual reproduction and the means by which the new individual is dispersed by angiosperms. Seed germination being the first step of plant establishment, the ultimate role of the transition between seed dormancy and germination during plant lifecycle is an important ecological and commercial trait. Last several decades, several environment factors have been reviewed to strongly effect the process of seed dormancy and germination. However, studies about seed response to temperature change are acute with the global warming. The aim of this work was to investigate temperature regulation of dormancy and germination in sunflower seeds. Proteomic analysis and enzyme profiling have been used to study metabolism regulation during seed dormancy release by temperature. Moreover, using molecular and cytological approaches, we investigate the interaction between temperature and phytohormones involved in this process. Our results revealed that temperature as an external factor to effect seed dormancy and germination by affecting, in one hand, the metabolism, and in the other hand the level and localization of major endogenous hormones
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Tavakkol, Afshari Reza. "Variation in seed dormancy of tetraploid wheat." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp03/NQ37916.pdf.
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Dzomeku, Israel K. "Modelling seed dormancy, germination and emergence of Striga hermonthica." Thesis, University of Reading, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.252261.
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Stutchbury, P. A. "The regulation of seed dormancy in the genus Acer." Thesis, University of Bristol, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.379534.
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Barros, Galvão Thiago. "Regulation of seed dormancy and germination in Arabidopsis thaliana." Thesis, University of York, 2016. http://etheses.whiterose.ac.uk/15593/.
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Seed germination is one of the most important developmental steps in the life cycle of a higher plant. Because of this, seed producing plants have evolved mechanisms, such as dormancy, that time germination based on environmental cues. The present study uses Arabidopsis thaliana as a model to address questions about seed dormancy and germination. Three different lines of investigation were followed. The first involved an investigation of how light quality regulates phytohormones in order to control germination. This identified a light-dependent mechanism that differentially regulates expression of the ALLENE OXIDE SYNTHASE and OXOPHYTODIENOATE-REDUCTASE 3 genes resulting in accumulation of cis-12-oxo-phytodienoic acid (cis-OPDA) and repression of seed germination under FR conditions. The second line of investigation involved a re- examination of the role of the ABSCISIC ACID INSENSITIVE (ABI) 5 and ABI4 transcription factors in regulating seed germination and oil mobilization respectively. The study found that abscisic acid (ABA) is able to block testa rupture in nicked seeds and this involves the ABI5, but not the ABI4, transcription factor. Furthermore, it was found that ABI4 is involved in the repression of ABA and cis-OPDA biosynthesis in a light- dependent manner, but has only a minor role in regulating oil mobilization in seeds. The third line of investigation focused on the regulation of dormancy during after-ripening and found that changes in phytohormone levels over an extended period can account for changes in dormancy state.
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Jayasuriya, Kariyawasam Marthinna Gamage Gehan. "COMPARATIVE BIOLOGY OF SEED DORMANCY-BREAK AND GERMINATION IN CONVOLVULACEAE (ASTERIDS, SOLANALES)." UKnowledge, 2008. http://uknowledge.uky.edu/gradschool_diss/639.
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The biology of seed dormancy and germination of 46 species representing 11 of the 12 tribes in Convolvulaceae were compared in laboratory (mostly), field and greenhouse experiments. Seeds were tested for kind of dormancy and storage behavior; artificial or simulated natural treatments were applied to break physical dormancy (PY); the initial route of water entry (“water gap”) into seeds was identified; the morphoanatomy of the water gap was compared in seeds of 17 species; ontogenetical differences between water gap and seed coat away from the hilum were described in Ipomoea lacunosa seeds; cycling of sensitivity to dormancy break was elucidated in seeds of I. lacunosa, I. hederacea, Cuscuta australis and Jaquemontia ovalifolia; and mechanism of opening of the water gap was determined for seeds of I. lacunosa and of I hederacea.
Seeds of only three of the 46 species were nondormant. Two of these were recalcitrant (Maripa panamensis and Erycibe henryi), and the other one was orthodox (Bonamia menziesii). Seeds of the other 43 species were orthodox and had PY except those of Cuscuta europea, which also had physiological dormancy (PD) i.e. combinational dormancy (PY + PD). Two bulges adjacent to the micropyle were identified as the water gap in all seeds with PY except those of Cuscuta, in which the hilar fissure is the water gap. Anatomy of the bulges (water gap) adjacent to the micropyle differs from that of seed coat away from the bulges. A different sequence and phase of anticlinal and periclinal cell divisions during development created weak transitional zones between bulge - hilum and bulge - seed coat away from hilum. Water vapor pressure changes below the bulges caused formation of the opening(s) in water gap. Seeds of I. lacunosa I. hederacea, C. australis and J. ovalifolia cycle between sensitive and insensitive states to dormancy break, but not between PY and nondormancy. Seed dormancy and storage characteristics and anatomy and morphology of dormancy of seeds of Convolvulaceae closely follow the molecular phylogeny of the family. I suggest that PY in seeds of subfamily Convolvuloideae evolved from nondormant recalcitrant seeds of an ancestor closely related to Erycibeae.
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Soltani, Ali. "Improvement of seed germination of Fagus orientalis Lipsky /." Umeå : Dept. of Silviculture, Swedish Univ. of Agricultural Sciences, 2003. http://epsilon.slu.se/s275.pdf.
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Holmberg, Kyle B. "SELECTION FOR REDUCED SEED DORMANCY IN SEVEN NATIVE GRASS SPECIES." MSSTATE, 2008. http://sun.library.msstate.edu/ETD-db/theses/available/etd-11052007-220827/.
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Lowland switchgrass (Panicum virgatum), big bluestem (Andropogon gerardii), indiangrass (Sorghastrum nutans), upland switchgrass (Panicum virgatum), little bluestem (Schizachyrium scoparium), beaked panicum (Panicum capillare), and purpletop (Tridens flavus) all show strong signs of seed dormancy which contributes to extremely poor field establishment. The objective of this work was to reduce seed dormancy by selecting individuals that exhibited reduced pre-stratification dormancy in laboratory tests. The classical breeding method of phenotypic recurrent selection was used to enhance germination. Of the three tall-stature species, lowland switchgrass made the greatest improvement in pre-stratification germination, followed by indiangrass and big bluestem. The four short stature species have shown various results after one cycle of selection at Starkville. A field emergence trial was also conducted to evaluate three cycles of breeding seed with five commercially available cultivars in which Cycle 3 seed produced more plants per hectare than any of the other cultivars or germplasm.
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Vasquez, Castillo Wilson Arturo. "Seed production, dormancy and commercialisation of Solanum phureja in Ecuador." Thesis, Imperial College London, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.415897.
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Wood, Laura Anne. "RELATIONSHIP BETWEEN ETHYLENE AND SEED DORMANCY RELEASE IN ECHINACEA SPECIES." UKnowledge, 2007. http://uknowledge.uky.edu/gradschool_theses/465.
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Inconsistent seed germination poses a problem for efficient seedling production of Echinacea species. Evidence suggests that ethylene can be effective for improving germination in Echinacea species. The objectives of this research were: to develop an ethylene pre-germination treatment that enhances germination in Echinacea species that is retained following drying and storage, and to determine if the ethylene effect on enhanced germination was an important mode of action for dormancy release. Four species of Echinacea (E. purpurea, E. tennesseensis, E. angustifolia and E. simulata) treated with 1-aminocyclopropane-1-carboxylic acid (ACC) or ethephon resulted in faster and generally higher germination. Pre-treatment of seeds with ACC or ethephon followed by drying was as effective as chilling stratification for enhancing germination depending on the species. While ethylene pretreatments did increase germination to some extent depending on species, it was concluded that 60-day stratification alone was a more commercially-viable treatment. Ethylene production or perception was not necessary for germination in untreated or stratified seeds as shown by aminoethoxyvinylglycine (AVG), silver thiosulfate (STS), and 1-methylcyclopropene (MCP) treatments. Both stratification and ACC treatment reduced Echinacea seed sensitivity to ABA and could be a common mechanism for enhanced germination. However, it does not appear that the increased germination seen after stratification was mediated through ethylene production because final germination percentages were generally unchanged following inhibition of ethylene production or action. In contrast, inhibition of ethylene production and perception reduced early 3-day germination suggesting that ethylene was more involved in seed vigor than final germination. It was determined that there is no physiological significance of ethylene for dormancy release in these Echinacea species.
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Kendall, Sarah. "Temperature regulation of seed dormancy and germination in Arabidopsis thaliana." Thesis, University of York, 2012. http://etheses.whiterose.ac.uk/3109/.
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The environmental regulation of seed dormancy and germination by temperature is an important process which allows the environmental conditions experienced by plants in the following generation to be controlled. Coping with temperature effects during seed maturation is essential for the consistent production of high quality seeds, but currently temperature signalling pathways in seeds are poorly understood. Previous work has shown that temperature during seed maturation regulates the levels of dormancy which are induced in the seed, although a mechanism for this pathway is currently unknown. Low temperature during imbibition promotes germination and although this is known to involve alterations to GA metabolism, again a mechanism is missing. Therefore, the aim of this study was to identify components of the mechanisms which regulate the temperature control of dormancy and germination in the model plant Arabidopsis thaliana. Cool and warm seed maturation temperatures induce high and low levels of dormancy respectively in Arabidopsis. These changes to dormancy levels are coupled with altered ABA and GA levels and gene expression controlling hormone synthesis and breakdown. Changes in maturation temperature do not appear to be linked to altered seed coat morphology or embryo development. During testing of cold-response mutants for dormancy phenotypes the expression of CBFs, a group of transcription factors which were characterised through the study of cold acclimation, was found to be necessary for dormancy. CBF RNAi and mutant seeds display reduced dormancy when matured at low temperature. However, the expression of CBFs is not promoted by exposure to low temperature in seeds, suggesting that this is not an important mechanism for the temperature control of dormancy. More strikingly, the E3 ligase HOS1 is absolutely required for high dormancy levels in response to low maturation temperature. hos1 mutants show a complete loss of dormancy when matured at any temperature and this phenotype is maternally inherited. The germination of hos1 seeds in the presence of PAC or ABA does not differ from wild-type, thus suggesting that sensitivity to GA and ABA is not altered in these seeds. However, levels of GA are increased in hos1 mutant seeds, which could be important for the reduced dormancy phenotype. The expression of TT genes, which are responsible for the accumulation of anthocyanidins in the seed coat, is downregulated in hos1 mutants and so could be involved in the regulation of dormancy by HOS1. Therefore; HOS1 defines a novel essential maternal pathway that regulates dormancy levels which involves the regulation of GA metabolism. A forward genetic screen identified a number of cold stratification insensitive (cosi) mutants. A thorough characterisation of these mutants revealed interesting phenotypes, but phenotypic variation and a lack of robust segregation data meant that the cosi mutants were not mapped.
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Just, Michael. "Seed morphology, dormancy and germination of South-West Australian Ericaceae." Thesis, Edith Cowan University, Research Online, Perth, Western Australia, 2018. https://ro.ecu.edu.au/theses/2051.
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The Ericaceae in South West Australia contains species with difficult to germinate seeds, including many species with deep intractable dormancy. A better understanding of seed biology and species specific dormancy, and germination mechanisms is required to overcome these difficulties. Land clearing, salinity and disease has resulted in over 125 species within 15 genera being listed as rare, highly restricted, threatened and endangered (Western Australian Herbarium 1998–). The present study examined the seed biology of eight species of Ericaceae native to Western Australia, exploring fruit and seed morphology, dormancy and germination. Cold and warm stratification was used in combination with gibberellic acid to classify dormancy. Among the two distinct fruit types that occur within the Ericaceae separate patterns of dormancy were found. Seeds held within a dehiscent capsule were found to possess non-deep and intermediate physiological dormancy whilst those within an indehiscent drupe possessed physiological and morphophysiological dormancy. Oxygen and nitric oxide enriched atmospheres, removal of seeds from endocarps and propagation from cuttings provided potential avenues for the propagation of study species.
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PETROLLINI, Elisa. "Medicago marina (L.) seed: unravelling mechanisms controlling germination and dormancy." Doctoral thesis, Università degli studi del Molise, 2012. http://hdl.handle.net/11695/66384.
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L’obiettivo generale di questo lavoro di tesi è studiare i complessi e poco conosciuti meccanismi che regolano la dormienza e la germinazione del seme di Medicago marina (L.), una specie mediterranea presente sulle coste dell’intera penisola italiana e che si è adattata a vivere in habitat specializzati come le dune.
I semi di questa specie sono caratterizzati da una forte dormienza che ne impedisce la germinazione e i risultati ottenuti durante il primo periodo del corso di dottorato, sono stati recentemente pubblicati (Scippa et al., 2011). I meccanismi che regolano dormienza/germinazione e la risposta agli stress dei semi di questa specie, sono stati studiati attraverso analisi fisiologiche e di proteomica. Fra i pretrattamenti utilizzati (scarificazione meccanica, congelamento a -20°C e riscaldamento a 100°C per un’ora), la scarificazione e il congelamento sono stati più efficaci nella rimozione della condizione di dormienza. Il ruolo dell’acido abscissico (ABA) è stato studiato attraverso un dosaggio immunoenzimatico (ELISA) che ha permesso di determinarne la concentrazione nei semi trattati, germinati e non germinati (semi maturi utilizzati come controllo). Fra tutti, la maggiore concentrazione di ABA è stata riscontrata nei semi sottoposti a riscaldamento, mentre il confronto fra la concentrazione di ABA raggiunta nei campioni germinati, di controllo e trattati ha fatto supporre che, nel seme, si attivino diverse vie di segnalazione in grado di regolare da un lato l’omeostasi dell’ABA in risposta a diverse condizioni di stress e dall’altro la germinazione. L’analisi del proteoma ha rivelato la presenza di 46 proteine espresse in maniera differenziale fra i campioni trattati e il controllo, di cui 14 sono state sequenziale e identificate attraverso spettrometria di massa. Diverse, fra le proteine identificate, sono importanti fattori di risposta a situazioni di stress, essendo coinvolte nel metabolismo dei lipidi, nel folding proteico e nella protezione della cromatina. L’analisi del fosfoproteoma ha dimostrato che la funzione di molte proteine, soprattutto nei semi sottoposti a riscaldamento, è modulata attraverso modificazioni post-traduzionali. Questi risultati lasciano presupporre che i semi di M. marina adottano una strategia di dormienza basata sulla presenza di robusti tegumenti (hardseededness) in grado di prevenire l’assorbimento di acqua e la germinazione; inoltre la dormienza può essere regolata da altri complessi meccanismi fisiologici, quali la termoinibizione.
Da questi primi risultati, si è portato avanti lo studio volto a definire il ruolo di controllo della dormienza e della germinazione da parte dell’endosperma micropilare. A questo scopo, utilizzando la tecnica del puncture force, è stato misurato il weakening dell’endosperma micropilare nei semi sottoposti a scarificazione meccanica e a trattamento con ABA durante un time course di circa 22 ore. L’effetto dell’ABA è stato valutato anche sulla velocità e sul tasso di germinabilità finale dei semi sottoposti a tale trattamento. I risultati ottenuti hanno dimostrato che l’ABA è in grado di provocare un ritardo sia del weakening dell’endosperma sia della velocità di germinazione, che si traduce a sua volta in una considerevole diminuzione della percentuale di germinazione finale. In seguito, attraverso l’analisi del proteoma e l’analisi statistica multivariata sono state individuate 95 proteine che potrebbero rappresentare markers specifici dei diversi stati fisiologici, quando, superata la fase di dormienza il seme si prepara per la germinazione. Risultati preliminari suggeriscono che l’endosperma micropilare può contribuire all’instaurarsi della condizione di dormienza fisica che, ancora una volta, può essere rimossa efficacemente attraverso la scarificazione meccanica; inoltre l’ABA può svolgere un ruolo predominante nella regolazione temporale della geminazione, agendo sul weakening dell’endosperma micropilare.The general aim of this thesis is to understand the complex and unknown mechanisms underlying dormancy and germination of Medicago marina (L.), a Mediterranean species distributed along the whole coasts of Italian peninsula and adapted to living in a specialized life habitats, like the dunes. Seeds of this species show strong dormancy that prevents germination. Results obtained during the first period of PhD program are published in a paper by Scippa et al., (2011). An integrated approach of physiological analyses and proteomics was used to investigate the mechanisms that control M. marina dormancy/germination and that underlie stress tolerance. First, was evaluated the effects on dormancy breaking of the following treatments: mechanical scarification, freezing at -20 °C, storage for 4 months and heating at 100 °C for 1 h. Mechanical scarification and freezing were the most effective treatments in overcoming dormancy. The role of abscisic acid (ABA) in M. marina dormancy was studied by ELISA immuno-enzymatic assay, determining the ABA content of germinated and non germinated mature (control) and treated seeds. The level of ABA was higher in treated seeds than in control seeds; the most significant increase occurred in the heated seeds. A comparison of the ABA level in the germinated, control and treated seeds suggests that different mechanisms modulate ABA content in response to different stresses, and that a specific ABA-signaling pathway regulates germination. Proteomic analysis revealed 46 proteins differentially expressed between treated and untreated seeds; 14 of these proteins were subsequently identified by mass spectrometry. Several of the proteins identified are important factors in the stress response, and are involved in such diverse functions as lipid metabolism, protein folding and chromatin protection. Lastly, an analysis of the phosphoproteome maps showed that the function of many proteins in seeds subjected to temperature treatment is modulated through post-translational modifications. Taken together, the data obtained showed that M. marina seeds adopt a dormancy strategy based on a hard seed coats, known as hardseededness, which prevent water uptake and germination; also, dormancy it can be regulated by other complex mechanisms beside seed coats, such as thermoinhibition, a delaying mechanisms of germination adopted by different species during late summer or early autumn. Starting from these first results, the PhD project proceeded in further investigations of mechanisms involved in the control of germination timing and dormancy establishment, due to the mechanical constraints of the micropylar endosperm, besides the seed coat. In order to accomplish this aim, the weakening of the endosperm was analyzed trough the puncture force measurements in seeds subjected to mechanical scarification and ABA treatment, along a 22 hours time course of imbibition. In addition to that, the effect of ABA and gibberellic acid treatments on germination rate and speed, were analyzed by performing germination test. Results obtained from the puncture force and germination tests for scarified seeds treated or not with ABA, revealed that the endosperm weakening, occurring in M. marina seeds before the germination, is delayed by ABA, which deferred also the germination of treated seeds. Then, the using of 2D analysis coupled whit the multivariate statistical analysis allowed the individuation of 95 spots that represent specific markers of different physiological states and might be expressed in seeds when dormancy is overcome in order to complete germination. First results suggest that the micropylar endosperm can contribute to the establishment of M. marina physical dormancy, that once again, it can be removed by mechanical scarification. Moreover, abscisic acid seems to be strongly involved in regulation of germination timing, by its action on micropylar endosperm weakening.
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Baker, Katherine S. "Seed germination and dormancy in south-western Australian fire ephemerals and burial as a factor influencing seed responsiveness to smoke." University of Western Australia. School of Plant Biology, 2006. http://theses.library.uwa.edu.au/adt-WU2007.0091.
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[Truncated abstract] Fire ephemerals are pioneer species that germinate in large numbers after fire and generally live for between six months and four years. Seeds produced during the short life span of these plants persist in the soil seedbank until a subsequent fire. This study examined the dormancy characteristics and germination requirements of ten Australian fire ephemeral species from five families. Seeds of four species germinated at one or more incubation temperatures in the laboratory, indicating that a proportion of their seedlots were non-dormant at the time of testing. Austrostipa compressa and Austrostipa macalpinei (Poaceae) produced >80% germination at 10?C and Alyogyne hakeifolia and Alyogyne huegelii (Malvaceae) produced 30-40% and 35-50% germination respectively at 10 to 25°C. In each of the Alyogyne species approximately 50% of seeds were impermeable to water, but scarification did not enable germination of all viable seeds suggesting that seeds which did not germinate, may have possessed physiological dormancy as well as physical dormancy. Remaining species had water permeable seeds. ... Germination of both Alyogyne species declined after six months of winter burial but was enhanced by heat treatments after a further six months of summer burial. Actinotus leucocephalus and Tersonia cyathiflora seeds exhibited annual dormancy cycling over two years of burial. Dormancy was alleviated over summer, allowing seeds of both species to germinate in smoke water when seeds were exhumed in autumn, and reimposed over winter, suppressing germination in spring. In Actinotus leucocephalus these dormancy changes were induced in the laboratory by warm (≥15°C) and cold (5°C) temperatures, alleviating and re-imposing dormancy, respectively. Wetting and drying seeds stored at 37°C further accelerated the rate of dormancy release. This dormancy cycling would increase the likelihood of seeds germinating when moisture availability in south-western Australia is greatest for seedling survival. It also explains the variation in germination response to smoke water observed in many species. Thus under natural conditions dormancy levels of fire ephemerals were altered during soil storage which enabled them to respond to fire-related cues such as heat and smoke water, and germinate in autumn. This information will assist in the use of these species in land rehabilitation and ornamental horticulture, and in the conservation of rare or endangered fire ephemerals.
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Jones, Stephen Keith. "Sitka spruce (Picea sitchensis [Bong.] Carr.) seed germination in relation to seed development, dormancy and storage." Thesis, University of Reading, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.283746.
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Favier, John F. "The effect of drying and storage regime on the germination of malting barley." Thesis, University of Newcastle Upon Tyne, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.238785.
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Bazaid, Salih Ali Mohamed. "Seed development and the induction of dormancy in the genus Acer." Thesis, University of Bristol, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.327965.
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Liu, Yinggao. "Molecular signaling in the seed dormancy release and germination in arabidopsis." HKBU Institutional Repository, 2009. http://repository.hkbu.edu.hk/etd_ra/1096.
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Lambton, P. A. "The photo-inhibition of seed germination and the induction of secondary dormancy." Thesis, University of Leicester, 1985. http://hdl.handle.net/2381/35323.
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A study of photoinhibition of seed germination and the induction of secondary dormancy has been made on weedy species that tend to produce large numbers of small, light-sensitive seeds. Both light-requiring (e.g., Chenopodium album) and light-inhibited (e.g., Amaranthus caudatus) species were used but nevertheless were found to show similar responses to high fluence irradiation, differences being largely ones of varying sensitivity. All species tested (except Digitalis purpurea) showed a marked inhibition of germination in continuous fluorescent white light supplemented with far-red compared to the response to fluorescent white light only. Urtica urens and A. caudatus germination, however, could be inhibited by fluorescent white light only and this response was dependent on both time and fluence rate. Interestingly, A. caudatus is a dark germinator whereas U. urens is light requiring (i.e., a small amount of light promotes germination but a large amount is inhibitory). The inhibitory action of prolonged light is dependent on photon fluence rate. In photoinhibition mediated through phytochrome cycling rate of the pigment appears to be important. However, cycling rate per se cannot explain all the observed responses; and the interuption of dark processes is another important factor. Cycling rate effects are increased when photoequilibrium is low. There is also a blue light photoreceptor of unknown form which shows fluence dependent characteristics in its photoinhibitory activity. Secondary dormancy is induced in seeds which have the ability to germinate but are prevented from doing so. In respect to the light environment, the same light conditions which inhibit germination also tend to induce secondary dormancy although there is no direct evidence on the action of blue light operating through the blue photoreceptor. The depth of secondary dormancy increases with the time of incubation in the inhibitory conditions and also is deeper for low photoequilibrium and high photon fluence rate. High photon fluence rate fluorescent white light inhibits the germination of U. urens but the high photoequilibrium established allows the seed to germinate in subsequent darkness. Photoinhibition of germination and induction of secondary dormancy have adaptive advantages for survival of the species since seedlings can avoid the competitive stresses of a stand of vegetation and the desiccating environment of the soil surface in full sunlight. Photoinhibition appears to act by preventing the active processes of germination from occurring, which thus enables the seeds to pass through cycles of hydration and dehydration without being damaged.
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Geyer, Regina [Verfasser]. "Molecular and cytological analysis of seed dormancy in Arabidopsis thaliana / Regina Geyer." Köln : Universitäts- und Stadtbibliothek Köln, 2008. http://d-nb.info/1013792696/34.
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Aroonrungshikul, Chuanpis. "Physiological and Biochemical Studies on the Seed Dormancy of Local Thai Cucumber." Kyoto University, 2002. http://hdl.handle.net/2433/150373.
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Schutte, Brian J. "Biology and ecology of Ambrosia Trifida L. seedling emergence." The Ohio State University, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=osu1181937971.
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Browning, Luke Wayne. "StCKP and potato tuber dormancy." Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/275074.
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Omami, Elizabeth Nabwile, of Western Sydney Hawkesbury University, of Agriculture Horticulture and Social Ecology Faculty, and School of Horticulture. "Amaranthus retroflexus seed dormancy and germination responses to environmental factors and chemical stimulants." THESIS_FAHSE_HOR_Omami_E.xml, 1993. http://handle.uws.edu.au:8081/1959.7/66.
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A large number of weed seeds in the soil persist because of seed dormancy, and depletion of the seed bank through manipulation of seed dormancy has been suggested as one of the goals in weed control. This study was designed to investigate some of the factors which control dormancy and germination in Amaranthus retroflexus seeds. Germination studies were conducted at different temperatures, and either in continuous white light or in the dark. Higher temperatures increased germination and, although light interacted with temperature, its effect on germination varied with the temperature. In an attempt to determine changes in dormancy during dry storage, two lots of seeds were stored dry at different temperatures. Loss in dormancy increased with an increase in storage temperature and duration, but the time required for maximum germination varied according to the seedlot. Seeds germinated to higher percentages at high temperatures, but storage at higher temperatures and for prolonged duration resulted in seeds gaining the ability to germinate at lower temperatures. Changes in dormancy under field conditions were also examined. Seeds were buried at different depths and for different durations and they all lost viability with time, but this loss was greater in surface-sown and shallowly buried seeds. Dormancy was broken during cold periods and induced as warmer periods progressed. The effects of chemical stimulants on dormancy and germination were investigated. The response of seeds to ethephon and nitrate were assessed at different temperatures either at continuous white light or in the dark. Germination increased with the concentration of the chemicals, and a greater response was observed at lower temperatures. The response to light varied depending on temperatureMaster of Science (Hons)
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Chen, Hua. "Seed dormancy of Pitcher's thistle, a threatened species of Lake Huron sand dunes." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape16/PQDD_0009/MQ28548.pdf.
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Shepherd, Sophie. "Genotype and environment interactions of seed dormancy in wild oat (Avena fatua L.)." Thesis, University of Reading, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.427855.
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Andriotis, Vasilios M. E. "Seed dormancy alleviation in Corylus avellana L. : phosphate pool and phosphate-mobilising enzymes." Thesis, University of Reading, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.250719.
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Bair, Necia B. "A hydrothermal after-ripening time model of seed dormancy loss in Bromus tectorum /." Diss., CLICK HERE for online access, 2004. http://contentdm.lib.byu.edu/ETD/image/etd487.pdf.
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Omami, Elizabeth Nabwile. "Amaranthus retroflexus seed dormancy and germination responses to environmental factors and chemical stimulants." Thesis, [S.l. : s.n.], 1993. http://handle.uws.edu.au:8081/1959.7/66.
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A large number of weed seeds in the soil persist because of seed dormancy, and depletion of the seed bank through manipulation of seed dormancy has been suggested as one of the goals in weed control. This study was designed to investigate some of the factors which control dormancy and germination in Amaranthus retroflexus seeds. Germination studies were conducted at different temperatures, and either in continuous white light or in the dark. Higher temperatures increased germination and, although light interacted with temperature, its effect on germination varied with the temperature. In an attempt to determine changes in dormancy during dry storage, two lots of seeds were stored dry at different temperatures. Loss in dormancy increased with an increase in storage temperature and duration, but the time required for maximum germination varied according to the seedlot. Seeds germinated to higher percentages at high temperatures, but storage at higher temperatures and for prolonged duration resulted in seeds gaining the ability to germinate at lower temperatures. Changes in dormancy under field conditions were also examined. Seeds were buried at different depths and for different durations and they all lost viability with time, but this loss was greater in surface-sown and shallowly buried seeds. Dormancy was broken during cold periods and induced as warmer periods progressed. The effects of chemical stimulants on dormancy and germination were investigated. The response of seeds to ethephon and nitrate were assessed at different temperatures either at continuous white light or in the dark. Germination increased with the concentration of the chemicals, and a greater response was observed at lower temperatures. The response to light varied depending on temperature
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Omami, Elizabeth Nabwile. "Amaranthus retroflexus seed dormancy and germination responses to environmental factors and chemical stimulants /." [S.l. : s.n.], 1993. http://library.uws.edu.au/adt-NUWS/public/adt-NUWS20030603.091907/index.html.
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Bair, Necia Beck. "A Hydrothermal After-ripening Time Model of Seed Dormancy Loss in Bromus tectorum." BYU ScholarsArchive, 2004. https://scholarsarchive.byu.edu/etd/533.
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After-ripening, the process of seed dormancy loss in dry storage is associated with a decrease in the mean base water potential, one of the parameters of hydrothermal time. The rate of change of the mean base water potential is assumed to be a linear function of temperature above a specific base temperature and as a result can be described by a thermal after-ripening (TAR) time model, an extension of hydrothermal modelling. The thermal requirement for after-ripening is the thermal time necessary for the modelling base water potential of the seed to shift from its original value to its final value. In order to include the effects of water potential on the rate of dormancy loss, a hydrothermal after-ripening (HTAR) time model was developed. Laboratory and field studies were conducted using seeds of Bromus tectorum. These studies identified four important ranges of water potential that influence the rate of dormancy loss. The ranges are identified as follows: seeds experiencing soil water potentials seeds experiencing soil water potentials <-400 MPa do not after-ripen, between -400 MPa and -150 MPa seeds after-ripen as a function of temperature (T) and water potential (Ψ), seeds experiencing water potentials >-150 MPa after-ripen as a linear function of temperature, and somewhere above -40 MPa seeds are too wet to after-ripen. These ranges suggest that specific reaction thresholds associated with non-fully imbibed seeds also apply to the process of after-ripening. The HTAR model for B. tectorum seeds generally improved predictions of dormancy loss in the field under soil conditions that were too dry for TAR alone. Reduced after-ripening rate under extremely dry conditions is ecologically relevant in explaining how seeds may prolong dormancy under high soil temperature conditions.
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Sautu, Adriana Elena. "ECOLOGY, MORPHOLOGY, AND GERMINATION PHYSIOLOGY OF TREE SEEDS IN A TROPICAL SEMIEVERGREEN FOREST IN THE PANAMA CANAL WATERSHED, WITH SPECIAL REFERENCE TO SEED DORMANCY CLASSES ALONG A PRECIPITATION GRADIENT." UKnowledge, 2004. http://uknowledge.uky.edu/gradschool_theses/206.
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The Panama Canal Watershed (PCW) represents a special opportunity for studies related to seed dormancy in the tropics with both applied and basic research objectives. There is a clear need for seed information for nursery planning in restoration projects that involves use of a large number of local species. Moreover, the strong rainfall gradient along the 60 km of continuous lowland forest in the PCW represents an excellent opportunity to understand dormancy and its role as an adaptive trait that evolved in response to environmental factors. This study presents useful seed information for 100 tree species native to the PCW. For each species, it includes collection system, fruiting time, seed mass, seed moisture content, germination, and longevity in storage at 20??C. For the first time, an attempt is made to classify (to class sensu Baskin andamp; Baskin 2004) the class of dormancy in seeds of the PCW. An analysis of the relationship between class of dormancy and seed mass, moisture content, longevity, germination patterns, and seasonality is presented. The relationship between class of seed dormancy and longevity and geographical distribution of species within the watershed based on the rainfall gradient was investigated.
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Arc, Erwann. "Étude de l'implication des oxides d'azote dans le controle de la dormance des graines d'Arabidopsis thaliana." Thesis, Paris, AgroParisTech, 2013. http://www.theses.fr/2013AGPT0011.
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Russell, Laurel. "Isolation and analysis of mutants in Arabidopsis thaliana disrupted in the transition between dormancy and germination." Thesis, University of Bristol, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.265420.
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Hamid, Shaikh Abdul. "Chemical and biochemical aspects of seed dormancy and recalcitrance in hazelnuts (Corylus Avellana L.)." Thesis, Teesside University, 2015. http://hdl.handle.net/10149/613551.
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Hazelnuts are mostly non-dormant at harvest but develop seed dormancy after a few days of storage. The seeds have been classified as recalcitrant since they cannot be stored for more than one year under ambient conditions. Cryopreservation has not been satisfactory so an alternative protocol is required. To test for recalcitrance, chilled non-dormant seeds (control) were compared with gibberellic acid (GA3) treated seeds during 6 weeks storage at 5°C or at ambient temperature. Control seed moisture content (MC) was 14-15% compared with 20% for GA3 treated seeds. No change in viability was noted until the end of 6 weeks at ambient temperature, when infection proliferated. Reduced germinability, associated with increased leachate conductivity, was noted on all treatments and controls, with ambient temperature storage most harmful for seed viability. This supports classification of hazel seeds as recalcitrant. However, orthodox behaviour could be induced by reducing seed moisture to <6%, showing survival for more than 3 years at -20°C with acceptable germinability and producing healthy seedlings. Pathogen tests show that 6 weeks chilling to break seed dormancy may activate the seeds’ internal protective mechanisms, thereby reducing infection and enabling germination and healthy seedling establishment. The link between seed viability and protection from free radicals and pathogens was examined. Antioxidant activity in hazelnut seed associates (such as endocarp, funiculus and testa) was found to be much higher than in the seed embryo, perhaps indicating that hazel seeds have natural protective mechanisms within the pericarp. Antioxidant activity of seed associates increased during chilling, indicating their role in protecting the seed. Nevertheless, TTC test revealed that seeds acclimatised to ii < 6% MC and stored at 5°C for 45 weeks showed viability loss due to damage of the embryonic axes, probably caused by free radicals. Initial tests to stabilise seed moisture content showed that reduction in seed moisture did not impose dormancy and seed moisture content (MC) stabilisation resulted in > 80% germination but many abnormal seedlings. Dormancy reversibility was tested by treatments T1 (one period at 15°C) and T2 (two periods at 15°C), designed following a consideration of the natural environment. Both resulted in reduced germination, delayed seedling emergence, increased abnormal seedlings, reduced seedling height and decreased internode numbers. To test the role of temperature in reduced seed performance, non-dormant hazelnuts were held at either 5°C or at ambient temperature for up to 6 weeks. Seeds from both sets exhibited high viability, but germinability was significantly decreased in the ambient temperature set, associated with increases in leachate conductivity and infection. Work in this thesis has confirmed that dormancy was broken by chilling, with gradually increasing germination as chilling time was increased. Germination increased with increase in chilling and reduction in infection. No infection was recoreded after 6 weeks chilling. It is most likely that protective agents are produced causing suppression of infection. In these experiments it was observed that not all germinated seeds produced healthy seedlings, suggesting that germination tests without observation of seedlings may give an incomplete assessment of germination success. Assessment using the Tetrazolium test (TTC) was found to be much more dependable and it was also possible to detect damage to specific tissues that might result in unhealthy seedlings.
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Soleimani, Mohammadreza. "The effect of rain and agronomy on seed dormancy and quality of winter cereals." Thesis, University of Reading, 2016. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.739381.
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Variation in agronomy and crop production environment often have interactive effects on cereal seed dormancy and seed and grain quality, possibly by effects on canopy temperature, seed size, or grain drying rate. The effect of rain, nitrogen (N) fertilizer, and fungicide on seed dormancy, grain quality and subsequent seedling growth of winter cereals was studied in three field experiments. Dormancy was released during seed development and maturation in barley, rye and triticale (2012) but released and then re-imposed in wheat (2012 and 2013). Dormancy release was stimulated in barley, rye and triticale, but not wheat, when crops were sheltered from rain in the field. Alpha-amylase activity was reduced and Hagberg falling number (HFN) increased by rain shelter in barley and wheat; HFN was associated positively with grain drying rate in barley and rye. Dormancy release in wheat was stimulated by fungicide application but delayed by early N. The latter increased sulphur and protein concentrations, HFN, and sodium dodecyl sulphate sedimentation volume. This effect was greater when fungicide and/or late N application were also applied. Fungicide improved subsequent seedling growth in wheat in 2012 only. Plumule and root length and dry weight were associated positively with seed size in both years. It is proposed that rain and N fertilizer delayed dormancy release through an indirect effect on grain drying rate and/or canopy temperature, whereas fungicide stimulated dormancy release by reducing grain surface fungal colonies. As expected, rain reduced but N fertilizer increased HFN, but treatment effects on grain drying rate and/or seed size could not account for all these effects on HFN. Fungicide increased subsequent seedling growth indirectly by increasing seed size in addition to a direct effect of fungicide on reducing infection on seedlings, but only when crop disease pressure was high (2012, not 2013).
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Marty, James. "Revegetation of Bulrushes Bolboschoenus Maritimus, Schoenoplectus Acutus, and S. Americanus in Great Salt Lake Wetlands: Seed Biology and Influence of Environmental Factors on Rhizomes." DigitalCommons@USU, 2016. https://digitalcommons.usu.edu/etd/5066.
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A primary goal of ecological restoration is to establish desirable plant species. This goal is particularly important following the removal of invasive plants. Understanding biological traits of plant species important to revegetation is crucial to plant establishment. In the globally important Great Salt Lake (GSL) wetlands, native habitat-forming bulrushes Bolboschoenus maritimus, Schoenoplectus acutus, and S. americanus are frequently displaced by the invasive grass Phragmites australis. Successful revegetation of bulrushes relies on improving our understanding of seed dormancy break, seed germination requirements, and the environmental factors affecting rhizome emergence and growth. We used a series of germination chamber and greenhouse experiments to examine effective seed dormancy break treatments and germination conditions for multiple collection sites of bulrushes B. maritimus, S. acutus, and S. americanus. We also performed a greenhouse experiment to investigate how water depth, nutrient, and salinity levels affect B. maritimus and S. acutus emergence and growth from rhizomes. Cold, moist stratification and bleach scarification were effective dormancy break treatments for all species, though magnitude of effect varied by species and source site. Soaking the seeds after application of dormancy break treatments improved germination for all species. Rhizome emergence of S. acutus was negatively affected by high water depth, likely due to oxygen limitation. Bolboschoenus maritimus was salinity tolerant relative to S. acutus. GSL wetland managers can use these findings to improve revegetation projects via seeding and planting.
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Postma, Froukje M. "Selection during Early Life Stages and Local Adaptation in Arabidopsis thaliana." Doctoral thesis, Uppsala universitet, Växtekologi och evolution, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-302862.
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Organisms are often adapted to their local environment, but the role of early life stages in adaptive differentiation among populations remains poorly known. The aim of my thesis was to investigate the contribution of early life stages to the magnitude and genetic basis of local adaptation, and to identify the underlying adaptive traits. For this, I used two natural populations of the annual plant Arabidopsis thaliana from Italy and Sweden, and a Recombinant Inbred Line (RIL) population derived from a cross between these populations. By combining greenhouse and field experiments, Quantitative Trait Loci (QTL) mapping, and path analysis, I examined (1) the genetic basis of seed dormancy, (2) the contribution of differential seedling establishment to local adaptation, (3) among-year variation in selection during seedling establishment, (4) direct and indirect effects of seed dormancy and timing of germination on fitness, and (5) the adaptive value of the seed bank. I found that both the level and the genetic basis of seed dormancy were affected by the maternal environment. One major-effect QTL was identified in all maternal environments, which overlaps with the dormancy gene DELAY OF GERMINATION 1 (DOG1). Selection through seedling establishment success contributed strongly to local adaptation and genetic tradeoffs, and varied among years. Variation in seedling establishment and overall fitness among RILs could be explained by genetically based differences in seed dormancy and timing of germination. Seed dormancy affected fitness throughout the life cycle, by affecting the proportion of germinated seeds, and indirectly via effects on timing of germination, plant size and flowering time. My results suggest that a considerable portion of A. thaliana seeds enter the seed bank. I found genetic differences in dormancy cycling behaviour between the two populations, which could contribute to local adaptation. The value of a seed bank should be higher at the Swedish study site than at the Italian study site due to lower rate of seed mortality in the soil. Overall, the results of this thesis demonstrate that early life stages contribute strongly to both the magnitude and the genetics of local adaptation.
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Contreras, Samuel A. "Effects of maternal plant invironment on lettuce (lactuca sativa l.) seed dormancy, germinability, and storability." The Ohio State University, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=osu1196451272.
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Santos, Marta Sofia Sousa. "Efeito de pré-tratamentos na germinação de sementes da espécie Corema album L.(subsp. album)." Master's thesis, ISA, 2013. http://hdl.handle.net/10400.5/6462.
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Mestrado em Engenharia Agronómica - Hortofruticultura e Viticultura - Instituto Superior de AgronomiaCorema album (Ericaceae) endemic of the Atlantic dunes of the Iberian Peninsula has the possibility to become a new niche berry crop. Considering the agronomic and market possibilities for this specie we characterized C. album populations along its biogeographical area. The results show that different seeds characteristics differ significantly between sites. We also tested the effect of pretreatments on the germination of C. album seeds (subsp. album). Seeds were collected from Duna de Quiaios in 2011, from Comporta in 2011 and Aldeia do Meco in 2011 and in 2012. The results show that there is site-to-site variation in the same year and year-to-year variation in a particular site in percentage of germinated seeds. Acid scarification (30, 60 and 120 minutes) followed by 1000 ppm of gibberellic acid was the most effective pretreatment in breaking dormancy of C. album and this pretreatment promote the best germination from seeds collected from Aldeia do Meco 2011 (30.3%) after 175 days. Our results suggest that the seeds had morphophysiological dormancy. Considering the 4600 seeds collected: 54.5% had ruptured the seed coat, 7.4% had germinated and seedling survival was 0.1%.
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Esser, Andrew Ross. "Maternal environmental factors influencing kochia (Kochia scoparia) seed characteristics." Thesis, Kansas State University, 2014. http://hdl.handle.net/2097/17750.
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Master of ScienceDepartment of Agronomy
Anita Dille
A better understanding of kochia (Kochia scoparia) seed characteristics is necessary for long term management of this increasingly troublesome weed. The objectives were to evaluate maternal environmental factors influencing kochia seed produced in the field and to document variability in dormancy and seed viability produced within a single kochia plant grown in the greenhouse or field. Field experiments were conducted in 2012 and 2013 at the Kansas State Agricultural Research Center in Hays. Two different kochia biotypes from Hays were planted with and without five canopy types, namely corn, soybean, grain sorghum, wheat stubble, and kochia plants. A greenhouse experiment with two generations (F1 and F2) of self-pollination was conducted with the same kochia biotypes. Date of initial flowering and final plant heights were recorded. Plants were harvested when seed was mature and divided into three equal parts (top, middle, and bottom). Seeds were cold treated or not, and approximately 50 seeds were placed in petri dishes with water for germination counts taken over six weeks. Viability of remaining seeds were then tested. For field-grown kochia, plants were taller in corn, sorghum and weedy canopies compared to the absence of a canopy. Seed germination from field grown kochia ranged between 77 and 100% for both treatments. There was reduced germination in the presence of a weedy canopy for both treatments and biotypes (77 to 82%) compared to the absence (93 to 99%), with an increase in hard viable seed in the presence of weedy canopy (5 to 14%). In the greenhouse, the F2 generation produced more immediately germinable seed compared to the F1 generation which had more seed with delayed germinability. Seed from bottom third of F1 and F2 plants had greater total germination (73 and 70%, respectively) compared to the middle (61 and 65%) and top (50 and 59%) thirds of the plant. There was a maternal environmental effect on kochia seed characteristics with implications on generating persistent seed for the future seedbank.
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Tilini, Kassie Lorraine. "The Seed Ecology of Rare and Endangered Gibbens' Beardtongue (Penstemon gibbensii) and Blowout Penstemon (Penstemon haydenii)." BYU ScholarsArchive, 2013. https://scholarsarchive.byu.edu/etd/4065.
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Penstemon gibbensii and Penstemon haydenii are two rare, perennial forbs inhabiting remote areas of the western United States. P. gibbensii is listed as a sensitive species by the Bureau of Land Management (BLM) in Colorado, Utah, and Wyoming (Heidel, 2009). P. haydenii was designated as Endangered by the U.S. Fish and Wildlife Service in 1987 (Heidel, 2012). This thesis research was geared toward helping land managers in their efforts to protect and rehabilitate these species by providing understanding on different aspects of their seed ecology. My first study was a laboratory experiment performed on P. gibbensii and P. haydenii seed germination response to moist chilling and dry after-ripening. Wild harvested seeds were subjected to moist chilling at 2-4 °C for 0, 4, 8, 12, and 16 weeks and held in dry storage for approximately 2 years to determine effective methods for breaking primary dormancy. P. gibbensii seed germination increased consistently with increased length of chilling up to 16 weeks and exhibited habitat-correlated variation in this response. P. haydenii seed germination increased from 1 to 100% germination with 4 weeks of chilling. P. haydenii germination was greatest (96%) when incubated under a cool, diurnally-fluctuating temperature regime (10-20 °C) and responded positively to dry storage, increasing germination from 0 to 15%. My second study was an in situ field study designed to characterize the active seed bank of P. haydenii. We set up a transect line across a P. haydenii population and measured the number of seeds entering the seed bank, lost to predation post-dispersal, and persisting in the seed bank. P. haydenii does not appear to form an ecologically significant seed bank. Approximately 140 seeds/ 10m2 could potentially enter the seed bank but only 1 seed in the upper 10cm of sand persisted. Heavy post-dispersal insect predation resulted in a decrease in viability of nearly 30% in exposed P. haydenii seeds after just 12 hours. My third study explored the effects of burial by sand on P. haydenii. Wild-harvested seeds were planted in pots at 1, 2, 4, 6, 8, and 10cm deep in sand and incubated at 10-20 °C. Seed germination and mortality and seedling emergence were measured. The response of dormant seeds to post-burial incubation was determined. Burial depth decreased seedling emergence and seed germination. Shallow burial appears to induce secondary dormancy for seeds that don't germinate quickly, whereas deep burial appears to impose enforced dormancy in burial.
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Galindo, Carlos Afonso Magalhães [UNESP]. "Absorção de água, germinação e dormência de sementes de mucuna preta." Universidade Estadual Paulista (UNESP), 2006. http://hdl.handle.net/11449/96798.
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Com o objetivo de estudar a dormência tegumentar e caracterizar possíveis relações entre tamanho e qualidade fisiológica e permeabilidade dos tegumentos, qualidade fisiológica e permeabilidade dos tegumentos, teor de água inicial e qualidade fisiológica de sementes de mucuna preta, foram conduzidos os seguintes experimentos: determinação do teor inicial de água dos lotes (RAS); DIC, 4 repetições de 25 sementes cada; peso de 100 sementes, 4x100, DIC; teste de %G e IVG 4x25 cada, DIC; 12 tratamentos para superação de dormência; classificação dos lotes em três classes de tamanho; teor inicial de água das sementes de diferentes tamanhos (RAS), DBC, repetições 4x25, fatorial 6 lotes x 3 tamanhos; curvas de embebição com dados em dispersão e uso de função polinomial de quarto grau, dados obtidos pela razão peso final(PF)/peso inicial(PI); teste de CE com repetições 4x25, DIC, fatorial 6 lotes x 3 tamanhos, substrato solo/areis. Os lotes apresentaram relação positiva inversa para teor de água inicial em relação à germinação; resultados dos tratamentos para superação de dormência com interações para lotes e para tamanhos dentro dos lotes; os testes demonstraram haver maior interação entre lotes, ocorrendo o contrário para a variável tamanho de sementes. Concluiu-se que: sementes pequenas são mais permeáveis em lotes não dormentes; entre lotes de germinações semelhantes o de menor teor de água inicial é o de maior vigor; sementes grandes produzem mais fitomassa e o tratamento mais eficiente para quebra de dormência foi escarificação com ácido sulfúrico concentrado (98%) por 7 minutos.
Aiming to study damage and characterize possible relationships between size and physiological quality; size and coat permeability; physiological quality and tegument permeability; initial content of water and physiological quality of mucuna preta sedes (Stizolobium aterrimum Pierce & Tracy) the following experiments were conducted: análisis of water content of seed lots by oven meted at 105°C during 24 hours using with four replications of 100 seeds each; germination test (%G) and speed of germination index (SGI) with four replications of 25 seeds in complete randomized design; twelve treatments to break dormancy The seed lots presented inverse positive relationship for water content related to germination; treatment to break dormancy with interaction between lotsand seed sizes within lots; the tests demonstrated higher interaction between lots, occuring the inverse for the variable seed size; the imbibition curve proved to be na important tool in studies related with tegument permeabillity and levels of vigor among lots. The following conclusion can be withdrawn form data: small sedes are more permeable in nondormant lots; seed lots with similar germination or with lower water content, higher is the vigor; large sedes produce higher amount of phytomass. The best treatment to break seed dormancy of mucuna preta seed was acid escarification during seven minutes.
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Tilsner, Heidy Rose. "Studies on the induction and release of seed dormancy in wild oats (Avena fatua L.)." Thesis, University of British Columbia, 1986. http://hdl.handle.net/2429/26092.
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The induction and release of secondary dormancy by anaerobiosis in genetically pure dormant (AN-51, Mont 73) and nondormant (CS-40, SH-430) lines of Avena fatua L. and the role of alternative respiration in the regulation of its primary and secondary dormancy were studied. These lines differed with regard to the optimal period of anaerobiosis necessary for induction of dormancy and/or the degree (% of seeds acquiring dormancy) and duration of dormancy induced. Secondary dormancy could be induced more effectively in after-ripened seeds of dormant lines than in nondormant lines where only a short-term dormancy could be induced (in 5-7 week old seeds). As with primary dormancy, wild oat biotypes exhibit genetic variability in their secondary dormancy behaviour and factors such as temperature can modify the expression of this trait. The germination stimulants kinetin, isopentenyl adenine, sodium azide, potassium nitrate and ethanol, which break primary dormancy in wild oats, stimulated germination of secondarily dormant seeds (line AN-51). Since these chemicals are structurally diverse, primary and secondary dormancies appear to be regulated by similar mechanism(s).
Salicylhydroxamate (SHAM), an inhibitor of alternative respiration, did not inhibit: 1. the respiration of embryos excised from after-ripened or secondarily dormant seeds, 2. the spontaneous release of secondary dormany in nondormant lines or 3. the release of secondary dormancy by a variety of chemicals (except azide), suggesting that alternative respiration is not involved in the induction or release of secondary dormancy.
Azide and cyanide released seed dormancy at similar concentrations and treatment durations. While cyanide released primary dormancy in seeds with little after-ripening, azide was effective only in secondarily dormant seeds or seeds with more extensive after-ripening. Both inhibitors stimulated seed respiration to a similar extent. The release of dormancy by cyanide was always preceded by respiratory stimulation, but the latter appeared to be independent of germination.
SHAM inhibited both the release of seed dormancy and the stimulation of seed respiration by azide but not by cyanide. Respiration was inhibited only when SHAM was applied concurrently with azide. When applied subsequent to azide treatment, SHAM had no effect. The respiration of seed pre-treated with azide and cyanide was insensitive to SHAM and therefore cannot be alternative.
Studies were performed to determine the effect of pH on the stimulation of germination and respiration by cytochrome oxidase inhibitors. Although pH had little effect on seed respiration and germination in controls and in the presence of cyanide, it strongly affected the activity of azide. At pH 5, 1 mM azide inhibited both seed respiration and germination whereas at pH 7 it stimulated both. SHAM at pH 7 did not affect the stimulation of respiration by azide, but inhibited it in the unbuffered system and at pH 5. Thus, SHAM appears to alter azide activity by lowering pH, increasing the concentration of undissociated (active) azide, which then completely inhibits cytochrome oxidase and consequently, seed respiration and germination. The release of dormancy and the stimulation of respiration by cyanide and azide do not appear to be related to the inhibition of cytochrome-mediated respiration or the stimulation of alternative respiration.Land and Food Systems, Faculty of
Graduate
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Contreras, Samuel A. "Effects of maternal plant environment on lettuce (Lactuca sativa L.) seed dormancy, germinability, and storability." Columbus, Ohio : Ohio State University, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1196451272.
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Carmona, Ricardo. "Factors affecting the efficacy of dormancy-relieving chemicals on weed seed banks in the soil." Thesis, University of Reading, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.316108.
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Correa-Morales, Ana Maria. "Unraveling the Genetics of Seed Dormancy in Barley Using Genome-Wide Association and Biparental Mapping." Diss., North Dakota State University, 2013. https://hdl.handle.net/10365/27232.
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Seed dormancy is the delay or inability of viable seeds to germinate under favorable conditions. The differential expression of dormancy levels in barley (Hordeum vulgare L.) seeds impacts malt quality. While dormant genotypes are required to avoid the incidence of preharvest-sprouting, genotypes with low dormancy are needed for uniform germination of seeds during malting. The objective of this study was to determine the genetic basis underlying seed dormancy in spring barley using genome-wide association mapping (AM) and linkage mapping. A panel of 3,072 elite U.S. spring barley breeding lines from eight breeding programs participating in the USDA-NIFA Barley Coordinated Agricultural Project and 193 F1-derived doubled-haploid lines from the cross `Stander'/ `Robust' were used to map QTL controlling seed dormancy. The AM panel and the doubled-haploid population were genotyped with SNP markers using the Illumina Golden Gate assay. Four mixed linear models that controlled population structure and kinship were used for the AM analyses, while composite interval mapping was used for the analysis of the biparental population. Our results confirmed the existence of marker-trait associations delineating two QTL regions in the long arm of chromosome 5H (5HL) using the AM panel, and a large effect QTL in the same region using the biparental population. The locations and effects of these marker-trait associations are congruent with previously mapped QTL for seed dormancy and demonstrate the two mapping methods effectively targeted the same genetic regions on the barley genome and provide insights about the genetics of seed dormancy.
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Taab, Alireza. "Seed dormancy and germination in Solanum nigrum and S. physalifolium as influenced by temperature conditions /." Uppsala : Dept. of Crop Production Ecology, Swedish University of Agricultural Sciences, 2009. http://epsilon.slu.se/200949.pdf.
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Naim, Elissa. "The oxidative modifications in the macromolecules of sunflower seed during germination." Electronic Thesis or Diss., Sorbonne université, 2018. https://accesdistant.sorbonne-universite.fr/login?url=https://theses-intra.sorbonne-universite.fr/2018SORUS536.pdf.
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Nos travaux ont porté sur la caractérisation des propriétés de la paroi cellulaire et de l’état d’oxydation des protéines, ainsi que sur leur relation avec la levée de dormance et le processus de germination. Ainsi, nous avons étudié le changement de résistance de la paroi cellulaire en utilisant différents traitements de levée de dormance: la post-maturation au sec, les espèces réactives de l’oxygène (reactive oxygen species, ROS) et une hormone (l’éthylène). L’étude du changement de résistance de la paroi cellulaire a montré une diminution de rigidité chez les graines traitées, capables de germer, par rapport à celles dormantes. La quantification des monosaccharides de la paroi n’a pas mis en évidence de différence significative, ce qui suggère l’absence de phénomènes associés au métabolisme des polysaccharides à ce stade de la germination sensu stricto. Seules les graines dormantes traitées avec les ROS ont présenté une diminution significative de l’activité de la pectine méthylestérase, une enzyme de la paroi connue pour son rôle dans l’élongation et la croissance. Une analyse immunocytologique a permis de décrire une paroi cellulaire plus estérifiée chez les graines dormantes. Ainsi, les ROS pourraient avoir une action non-enzymatique alors que l'éthylène pourrait agir en synergie avec les ROS afin d'obtenir le relâchement nécessaire de la paroi cellulaire pour la croissance. En outre, une analyse protéomique combinant la technique chromatographie à une analyse LC-MS / MS a été utilisée sur des graines de tournesol dormantes et non dormantes à différents temps d'imbibition afin d’identifier des protéines contenant des méthionines sulfoxydées, une oxydation protéique réversible. Des analyses préliminaires suggèrent un niveau d'oxydation des protéines au niveau de la méthionine plus important dans les graines non dormantes. De façon intéressante, de nombreuses protéines cibles de l’oxydation de la méthionine sont liées à de différents processus biologiques (traduction, métabolisme des protéines, énergie et le métabolisme, processus d’oxydo-réduction) connus pour être des acteurs impliqués dans la germination, suggérant ainsi l’importance de l’oxydation de la méthionine dans la régulation de différentes voies cellulaires impliquées dans la levée de dormance et la germinationOur work focused on the relationship of cell wall properties and protein oxidation state on dormancy alleviation and germination process. Different dormancy alleviation treatments have been used: afterripening, reactive oxygen species (ROS) and hormone (ethylene). Thus, the study of the change in resistance of the cell wall has shown a decrease in rigidity in treated seeds, able to germinate, compared to dormant ones. Quantification of the identified cell wall monosaccharides did not show any significant difference suggesting the absence of phenomena related to the metabolism of polysaccharides at this stage of germination sensu stricto. Only dormant seeds treated with ROS showed a significant decrease in pectin methylesterase activity, a cell wall enzyme known for its role in elongation and growth. An immunocytological analysis has described a more esterified cell wall in dormant seeds. Thus, the ROS could have a non-enzymatic action while ethylene could act in synergy with the ROS to fulfil the needed relaxation of the cell wall for growth. In addition, a proteomic analysis combining the diagonal chromatography technique with an LC-MS / MS analysis was used on dormant and non-dormant sunflower seeds at different imbibition times in order to identify proteins containing methionine sulfoxyde, a type of reversible protein oxidation. Preliminary analyzes suggest a higher level of protein oxidation in non-dormant seeds. Interestingly, many proteins affected by the oxidation of methionine are related to different biological processes (translation, protein metabolism, energy and metabolism, oxidation-reduction processes) known to be involved in germination, thereby suggesting the importance of methionine oxidation in the regulation of different cellular pathways involved in dormancy emergence and germination
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Salazar, Ana. "Seed Dynamics and Seedling Establishment of Woody Species in the Tropical Savannas of Central Brazil (Cerrado)." Scholarly Repository, 2010. http://scholarlyrepository.miami.edu/oa_dissertations/371.
Full textAbstract:
Studies of seed dynamics and seedling establishment at the community level in savanna ecosystems are scant, particularly in the tropical savannas of Central Brazil. The Brazilian savannas (cerrado) have the largest diversity of plant species among Neotropical savannas. Cerrado vegetation exhibits consistent changes in tree density and tree size along shallow topographic gradients. Vegetation types differ from closed savannas with high tree density, and a nearly continuous canopy cover in the uppermost portions, to open savannas with scattered short trees in the low portions of the topographic gradients. Whether or not dynamics of seeds and seedlings of woody species are consistent with variations in tree density and tree canopy cover across the cerrado landscape has not been determined, but could potentially influence such spatial patterns of tree density and canopy cover. The main objective of this study was to evaluate seed dynamics (i.e., seed rain, soil seed banks, and seed characteristics) and seedling establishment of woody species in three major cerrado vegetation types (closed, intermediate and open savannas) which differ in tree canopy cover and tree height. These vegetation types are located along topographic gradients of approximately 30 m in elevation and 1000 m in length. I conducted field work from June 2005 to August 2008 at the Instituto Brasileiro de Geografia e Estatística (IBGE) reserve, a field experimental station located 35 Km south of Brasilia, Brazil (15˚ 56' S, 47˚ 63' W, altitude 1100 m). I established permanent plots in each of the three vegetation types to assess seed rain, seed limitation, seed predation, and seed removal. I also quantified density and composition of the soil seed bank in each vegetation type and studied seed characteristics (i.e., kind of dormancy, moisture content, longevity) of 14 common cerrado woody species. In the field, I quantified establishment of woody seedlings in fire-protected savannas as well as in accidentally burned and frequently burned savannas. In the greenhouse I performed experiments to evaluate the effect of litter cover and light level on seedling emergence of 9 common cerrado woody species. Finally, I evaluated the effect of pulses of heat on seed germination of 5 common cerrado woody species under controlled conditions. The overall results of this study show that regardless of tree canopy cover, cerrado vegetation types are limited in seeds and seedlings of woody species, but these limitations are higher in open than in closed savannas. Most woody species do not form persistent soil seed banks along cerrado vegetation types because their seeds are short-lived, predated and quickly removed from the ground. In addition, dispersal season and dormancy appear to control timing of germination at the onset of the rainy season to ensure survival of seedlings in the field. In the absence of fire, establishment of woody seedlings is higher in closed than in open savannas because canopy cover mitigates the stressful environmental conditions of open savannas and thus facilitates establishment of woody seedlings. As a result, closed savannas are likely to maintain higher density of woody elements over time than open savannas. In burned savannas, however, species composition of woody and herbaceous seedlings is significantly affected because establishment of seedlings of woody and herbaceous species decreases but vegetative reproduction increases. This dissertation study indicates that interactions of early life-history stages of woody species with environmental and disturbance factors appear to play a more significant role in maintaining woody cover variations along cerrado topographic gradients than previously recognized.