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.

Seed dormancy is a mechanism with great importance in plant fitness and it inhibits seed germination until is broken and seeds can germinate under optimal environmental conditions favorable for successful reproduction. Primary dormancy is contingent to the environment that seeds and the mother plant experience. Temperature is a major factor participating in the regulation of this complex trait. High and low levels of dormancy are induced during seed maturation by cold and warm temperatures respectively but the mechanism at the basis of temperature signaling in seeds is not well understood. Climate change and increased weather variability threaten the constant supply of high quality seeds into the market hence agriculture productivity. Therefore, understanding and taking control of the molecular mechanism behind the regulation of seed dormancy and germination will help to control and predict seed behavior in the field. Here I describe and discuss a forward genetic screen for the selection of mutant seed lines with altered seed dormancy in response to cool temperature during seed set. Putative mutant seed lines designated awake1 to awake52, were preliminarily characterized. Eleven awake lines were selected for further analysis and one was investigated in more detail. It was revealed that awake1 seeds shares common phenotype with seeds of a suberin deficient mutant which were previously reported to display increased dormancy but, here, I show they also display a reduction of seed dormancy. Segregation analysis suggests that the reduced dormancy phenotype is maternally inherited as the suberin deficient mutants. Also, transcriptomic analysis shows that many suberin associated genes are temperature-regulated. I conclude that control of suberin deposition may play a role in the regulation of dormancy in response to cool temperature.

>The selection and development of species adapted to extreme conditions is very important for sustainable production in South Africa. This is due to South Africa¡¦s limited natural resources, low and unpredictable rainfall, and ever-increasing human population. The need for an increase in livestock production, collapsing grain markets and the difficulty of profitable maize production, places more importance on the role planted pastures will play in the future. Urochloa brachyuran is an annual tropical grass collected in Gauteng Province and selected for yield and quality. Seed harvested in 1999/2000 generally had a poor germination performance. This prompted an investigation into possible causes for poor germination and ways of improving seed quality. Investigating drying procedures, showed that drying temperatures between 20„aC and 45„aC did not have an effect on the quality of the seed. Several dormancy-breaking procedures were carried out with no success, although, applying a temperature treatment of 45„aC for three weeks, increased germination to between 30 and 40%. It was found that emergence of seedlings where seed was covered with soil, was significantly better than the control which was not. The highest germination was found when seeds were planted 30 mm deep. Conducting a water stress experiment proved that water deficits had a definite negative influence on the dry matter production and the seed production of U. brachyuran and can thus have a strong negative impact on the successful re-establishment of this annual species in water stressed conditions. A trial to evaluate dry matter production over three seasons was conducted in Pretoria. Representative samples were analysed for crude protein content and in vitro digestibility. The potential seed production was also evaluated over two seasons. Dry matter production results confirm results reported by Pieterse (1999), with an average total production of 14.3 t/ha, a digestibility of 74.9%, and a crude protein content of 12.3%. An average of 305kg seed/ha was produced over two seasons. The potential that U. brachyuran already holds for use in rehabilitation practices because of its fast, low growing habit, was further evaluated by the determination of the influence of saline mine water on germination and dry matter production. The results suggest that U. brachyuran can successfully be irrigated with saline mine water. It can be concluded from the results of this project that U. brachyuran can be successfully incorporated in animal production systems and rehabilitation practices. / Dissertation (MSc (Pasture Management))--University of Pretoria, 2007. / Plant Production and Soil Science / unrestricted

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京都大学 / 0048 / 新制・課程博士 / 博士(医学) / 甲第22307号 / 医博第4548号 / 新制||医||1040(附属図書館) / 京都大学大学院医学研究科医学専攻 / (主査)教授 武藤 学, 教授 松田 道行, 教授 髙折 晃史 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM

Resumo: O objetivo deste trabalho foi determinar técnicas eficientes para armazenar as sementes de umbu de modo a promover e uniformizar a germinação. As sementes foram armazenadas por 180 dias em sacos de papel mantidos em cinco condicões de ambiente: laboratório (25 ºC e 55% UR); estufa morna (40 ºC e 53% UR); estufa quente (50 ºC e 49% UR); câmara seca (18 oC e 65% UR) e câmara fria (10 oC e 65%UR). O potencial fisiológico foi avaliada a cada 60 dias por meio dos seguintes testes e determinações: teor de água; teste de germinação (25 ºC, avaliado semanalmente até 91 dias após a semeadura); teste da primeira contagem (14 dias); índice de velocidade de germinação; tempo médio de germinação e condutividade elétrica. Sementes armazenadas em estufa a 50 ºC e câmara fria a 10 oC ocasionaram reduções significativas da germinação. O armazenamento das sementes de umbu em laboratório ou em estufa morna (40 ºC) foram técnicas eficientes para promover a germinação; nestas condições, após seis meses de armazenamento, a germinação aumentou de 53% para 84 e 74%, respectivamente. / Abstract: The objective of this project was to determine efficient techniques to store "umbu" seeds so as to promote and uniformize germination. The seeds were stored for 180 days in paper bags which were placed under the following conditions : environmental (laboratory) conditions (25 °C and 55% of RH), mild temperature (40 °C and 53% of RH), high temperature (50 °C and 49% of RH), dry chamber (18 °C and 65% of RH), and cold chamber (10 °C and 65% of RH). Seed physiological potential was evaluated each 60 days by means of the following procedures : seed water content, seed germination (25 °C and 55% of RH) evalutated weekly up to 91 days after sowing, first count of germination (14 days), speed of germination index, mean time for germination, and electrical conductivity. Stored seeds in oven at 50 ºC and cold chamber at 10 °C caused significant reductions in germination. The storage of "umbu" seeds under environmental (laboratory) conditions or in an oven under 40 °C were techniques efficient enough to promote seed germination. Under those conditions, after six months of storage, seed germination increased from 53% to 84 and 74%, respectively / Mestre

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.

To persist in extreme environments, some meiofaunal taxa have adopted outstanding resistance strategies. Recent years have seen increased enthusiasm for understanding extreme-resistance mechanisms evolved by tardigrades, nematodes and rotifers, such as the capability to tolerate complete desiccation and freezing by entering a state of reversible suspension of metabolism called anhydrobiosis and cryobiosis, respectively. In contrast, the less common phenomenon of diapause, which includes encystment and cyclomorphosis, is defined by a suspension of growth and development with a reduction in metabolic activity induced by stressful environmental conditions. Because of their unique resistance, tardigrades and rotifers have been proposed as model organisms in the fields of exobiology and space research. They are also increasingly considered in medical research with the hope that their resistance mechanisms could be used to improve the tolerance of human cells to extreme stress. This review will analyse the dormancy strategies in tardigrades, rotifers and nematodes with emphasis on mechanisms of extreme stress tolerance to identify convergent and unique strategies occurring in these distinct groups. We also examine the ecological and evolutionary consequences of extreme tolerance by summarizing recent advances in this field.

Globally, mining is vital to human interests, but its practice can cause landscape alteration which may look unnatural or engineered. The reintroduction of native plants to these areas is needed to restore the visual appeal and ecological function back into these altered mine lands. Cercocarpus ledifolius (curl-leaf mountain mahogany) is one desirable native species in the Intermountain West that is prized for its potential to grow on step and rocky hillsides and for the habitat it provides for wildlife. Unfortunately, C. ledifolius does not establish well from seed, which has been attributed to seed dormancy. The first objective of this study was to determine if scarification and gibberellic acid (GA3) treatments improve germination by alleviating seed dormancy. We also aimed to determine if a combination of fungicide and hydrophobic seed coatings increased emergence and establishment of C. ledifolius seedlings in mine overburden by reducing loss from fungal pathogens and premature germination. We found that two treatments, GA3 and GA3 + hydrophobic coatings, improved emergence compared to untreated seed, producing 1.8 (P = 0.0682), and 2.2 (P = 0.0751) more seedlings per meter, respectively. The second objective of this study was to make improvements in the laboratory to treatments explored in the field trial. We found that C. ledifolius seed responded inconsistently to treatments applied in the lab. The 15-minute acid scarified seed in combination with various GA3 seed coatings had significantly higher germination than untreated seed in one trial but had no difference in a second trial. Overall, these results indicate that seed enhancement technologies have the potential to improve C. ledifolius emergence in reclaimed mine lands, but additional research is needed to understand the species' dormancy characteristics better and improve the efficacy of the applied seed treatments.

In malting barley, rapid germination is desirable and linked to end use quality. Modern malting varieties have been bred for low seed dormancy leading to issues with pre-harvest sprouting in wetter growing regions. To maintain malting capacity while minimizing germination on the maternal plant requires in-depth understanding of the genetic regulation of dormancy in malting barley. Currently, the major effect QTLs SD1 and SD2 have been shown to influence dormancy across multiple populations of barley, though the physiological mechanisms involved remain unclear. To search for novel genetic regions that influence primary dormancy, three mapping populations were assessed including two Canadian biparental populations (Synch and Legci) as well as a diversity panel sourced from multiple locations worldwide (ICARDA AM-14). The SD2 locus had a major effect in the Synch population while the SD1 locus had a major effect in the Legci population and neither SD1 nor SD2 were linked to dormancy in the diversity panel. Instead, 14 additional marker trait associations were identified in AM-14 suggesting that investigating a broader range of genetic regulation of dormancy outside of North American varieties may provide solutions to regulate this trait. Additional testing on SD1 revealed that variation at this locus did not affect ABA sensitivity during germination or GA or ABA-regulated gene expression during grain fill. Indeed, lines containing the non-dormant SD1 allele germinate at a similar rate as the dormant SD1 seeds when the glumella was removed from the embryo. This indicated that the effect of the alanine aminotransferase gene underlying the SD1 allele is dependent on physical restriction on the embryo or the hypoxic effects produced by the glumella. Imposing a hypoxic (5% oxygen) environment on exposed embryos revealed an association between non-dormancy at SD1 and reduced sensitivity to the suppressive effects of hypoxia on germination. This suggests that alanine aminotransferase regulates dormancy release during barley germination at least in part through regulation of the seed’s response to hypoxia.