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The plant species Sesbania tomentosa ('ōhai; Fabaceae) is endemic to the Hawaiian Islands, federally listed as endangered in the USA and has been proposed for categorization as Vulnerable on the IUCN Red List. In 2021, c. 12,000 seeds from 12 seed lots collected during 1990–1992 from across the Hawaiian Islands were discovered in ambient herbarium conditions (55% relative humidity (RH) at 20 °C). International gene bank standards suggest drying seeds in equilibrium with 15% RH and stored at −18 °C. To investigate seed viability, we mechanically scarified then sowed 15 seeds from each accession at daily alternating regimes of 12 h light and 12 h dark at temperatures of 25/15 °C, respectively. Germination was observed after 7 days and ended after 34 days. Mean final germination was 88.9 ± SD 0.1% (range 73–100%). Each seed lot was accessioned into the National Tropical Botanical Garden's Seed Bank and Laboratory. In seeds with a water-impermeable seed coat (i.e. physical dormancy), such as S. tomentosa , seeds can desorb but not absorb water. Therefore, if the seeds were initially dried, although exposed to high RH for up to 32 years, seed equilibrium RH may have remained low, which may in part explain the observed high germinability. This study holds significance for managers who are working to conserve this endangered Hawaiian species and suggests that even suboptimal conditions may still yield highly viable seeds several decades into the future. [ABSTRACT FROM AUTHOR]

This work provides insights into the deterioration of cacti seeds of Escontria chiotilla (F.A.C. Weber ex K. Schum) and Stenocereus pruinosus (Otto ex Pfeiff.) Buxbaum stored ex situ at 25 °C, under dry and dark conditions or buried in situ conditions in a xerophytic shrubland. Viability, germination speed, electrolyte leakage and indicators of the redox balance including glutathione content, glutathione half-cell reduction potential (E GSSG/2GSH) and malondialdehyde (MDA), oxidized protein content, together with water-soluble antioxidant enzyme activity were assessed. Over a period of two years of storage, viability was maintained when seeds were stored ex situ at 7–9% water content compared to seeds buried in the soil. A second burial experiment showed that seeds of E. chiotilla maintained viability during a year of storage that included a rainy season followed by a dry season. Thereafter, they died rapidly during the second rainy season. In contrast, those of S. pruinosus started to lose viability after 6 months of burial at the end of the rainy season and were mostly dead at the end of the dry season. This difference in persistence between species was related to a difference in the glutathione content and antioxidant enzyme activities. In both storage experiments, the loss of viability of both species was associated to a E GSSG/2GSH shift to a more oxidative state during burial. Yet, contents in MDA and oxidized soluble proteins were not related to redox imbalance and loss of viability, indicating that these compounds are not good markers of oxidative stress in cacti seeds during storage. [ABSTRACT FROM AUTHOR]

The germination percentage (GP) is commonly employed to estimate the viability of a seed population. Statistical methods such as analysis of variance (ANOVA) and logistic regression are frequently used to analyse GP data. While ANOVA has a long history of usage, logistic regression is considered more suitable for GP data due to its binomial nature. However, both methods have inherent issues that require attention. In this study, we address previously unexplored challenges associated with these methods and propose the utilization of a likelihood ratio test as a solution. We demonstrate the advantages of employing the likelihood ratio test for GP data analysis through simulations and real data analysis. [ABSTRACT FROM AUTHOR]

Understanding seed moisture desorption and adsorption isotherms is important for seed quality maintenance and better predicting seed storage lifespan. Freshly harvested oilseed rape and barley seeds were dried and then rehydrated twice. Seed equilibrium relative humidity (eRH) and moisture content (MC) were determined at different humidity levels so that two cycles of desorption and adsorption could be constructed. In addition, seeds were dried to 30% RH and then rehydrated to 50% RH for five cycles to determine whether they shift to the adsorption isotherm. Monolayer MC was determined using the Gugenheim-Anderson-de Boer model. Storage experiments were conducted for seeds equilibrated at 30, 40, 50, 60 and 70% RH for two cycles of desorption and adsorption at 45°C. Isotherm curves' shapes were similar for oilseed rape and barley, although spanning a greater MC range in barley. The hysteresis effect was observed for oilseed rape and barley seeds when dried over silica gel at <10% RH. However, this effect was only observed for barley seeds when dried to 30% RH, but not for oilseed rape seeds. Longevity was greater for adsorbing seeds than desorbing seeds at a given eRH, however, there was no significant difference in σ (the standard deviation of the normal distribution of seed deaths over time)–MC log–log relationship. The relationship shifted for seeds on the second cycle. In conclusion, if seed lots are stored at a specific RH, reaching equilibrium by desorption or adsorption can strongly influence their longevity. Also, when seeds of different species are dried to low RH, they will respond differently to a subsequent increase in RH, which could profoundly affect their longevity. [ABSTRACT FROM AUTHOR]

The obligate root parasite Cistanche armena is a recently rediscovered, extremely rare endangered species endemic to Armenia, specifically parasitizing camelthorn (Alhagi maurorum , Fabaceae) and saltwort (Salsola dendroides , Chenopodiaceae). Its populations are reputedly declining due to habitat destruction and biotic impacts. Since the only known means of its reproduction is via the seeds, understanding the mechanisms of breaking C. armena seed dormancy and germination along with the related aspects of the species' biology is highly important both from fundamental (functional ecology and evolution) and applied (conservation and management) perspectives. Here, we present the first in vitro seed germination protocol for C. armena involving fluridone, a systemic herbicide targeting the carotenoid biosynthetic pathway. In addition, the seed micromorphology of C. armena is described using both light microscopy and lignin autofluorescence visualized by confocal laser scanning microscopy. The actin cytoskeleton in radicle cells of germinated C. armena seedlings is described for the first time, being the proof of seed viability. Further elaboration and application of the proposed germination protocol with the cultivation of C. armena on susceptible hosts are altogether seen as a valuable tool for the conservation of this species. [ABSTRACT FROM AUTHOR]

Cumulative oxidation of cellular macromolecules during storage reduces seed longevity. This study was undertaken to unravel the physiological and biochemical changes in rice seeds that contribute to deterioration during storage. Rice seeds maintained at three different seed moisture contents (SMC; 10, 12 and 14%) were stored in airtight glass jars. Half of the jars were flushed with nitrogen gas to provide modified oxygen conditions, while the other half were sealed with natural air (21% O2). Seed quality in terms of germination and antioxidant defence mechanisms was monitored after 3 and 6 months of storage at 25°C. The results showed that seeds performed better when stored at low SMC (10 and 12%), whereas the deterioration process accelerated in seeds stored at higher SMC (14%). Coupling high SMC with the availability of oxygen in the storage environment produced a negative effect on seed quality and longevity. Results from the antioxidant analysis showed more activity in seeds stored with oxygen at high SMC (14%) compared to lower SMC stored in modified oxygen conditions. Therefore, it is recommended that storage with low moisture levels (12%) or below (10%) is the best to preserve rice seed quality. However, at higher moisture levels (14%), the availability of oxygen in storage is more harmful to seed lifespan and quality. [ABSTRACT FROM AUTHOR]

Understanding the relative longevity of different seed lots, perhaps of different species or genotypes, but also following production under different environments or using different cultivation methods, or following different post-harvest treatments, is relevant to anyone concerned with the retention of seed lot viability and vigour during storage. However, different scientists over the years have used different conditions to assess seed lot longevity, as well as different variables as the measure of 'longevity.' Here, we give some of the backgrounds to how two standard protocols, with an open and closed system respectively, were derived, and explain why we consider p 50, defined as the time during storage when seed lot viability, as measured through a germination test, has declined to 50%, is a suitable longevity trait parameter. [ABSTRACT FROM AUTHOR]

The J. Derek Bewley Career Lectures presented at the triennial meetings of the International Society of Seed Science support early-career seed scientists by providing retrospective views, from those late in their careers, of lessons learned and future implications. Ambition, ability, inspiration, foresight, hard work and opportunity are obvious career requirements. The importance of mentoring and teamwork combined with the clear communication of results, understanding and ideas are emphasized. The role of illustration in research, and its dissemination, is outlined: illustration can support hypothesis development, testing and communication. Climate change may perturb the production of high-quality seed affecting conservation as well as agriculture, horticulture and forestry. An illustrative synthesis of the current understanding of temporal aspects of the effects of seed production environment on seed quality (assessed by subsequent seed storage longevity) is provided for wheat (Triticum aestivum L.) and rice (Oryza sativa L.). Seed science research can contribute to complex global challenges such as future food supplies from seed-propagated crops in our changing climate whilst conserving biological diversity (through seed ecology and technologies such as ex situ plant genetic resources conservation by long-term seed storage in genebanks), but only if that research can be – and then is – applied. [ABSTRACT FROM AUTHOR]

To maximize seed longevity, seeds should be harvested at optimal maturity, that is, when seeds have acquired maximum physiological quality before deterioration begins. The aim of this study was to map the variation in temporal patterns of lentil (Lens culinaris Medik.) seed quality development when grown across four regeneration environments, which differ in the level of temperature and humidity control throughout the growing season, at the Australian Grains Genebank. Seeds of two lentil accessions (76080 and 76072) were harvested at different stages throughout development, commencing at 21 d after 50% anthesis until a maximum of 130 d. At each harvest, physiological quality traits, including germinability (fresh and dried seeds) and seed longevity, were determined, as well as seed dry weight and moisture content. Seeds of both accessions, and in all environments, started to accumulate physiological quality early on in development but did not reach their maximum until 3–54 d after mass maturity. The temporal patterns of desiccation tolerance and storage longevity were highly influenced by the environmental conditions during the maturation drying phase, affecting both 'when' maximum quality was attained and for how long it was maintained, thereafter. Seeds did not show a typical developmental response, rather variation was observed in seed quality development both between and within accessions grown in the different environments. The poorest storage longevity was seen when seeds of both accessions were grown in the cooler, temperature-controlled glasshouse, and the maximum longevity was observed in the warmer, semi-protected environments of the green and the big igloo for accessions 76080 and 76072, respectively. [ABSTRACT FROM AUTHOR]

Serotiny is a strategy in which the retention of mature seeds in parent structures allows plants to cope with environmental variability like heat, drought or fire. Although this phenomenon might be common in Cactaceae, and particularly in Melocactus, it has generally been scarcely addressed. The main goal of our work is to investigate if there are seeds hidden in the cephalium of Melocactus matanzanus and if there are, determine whether or not these seeds maintain their viability. We also discuss some advantages the cephalium may offer as diaspore after the death of individuals. Cephalia collected from dead individuals were divided into four slices and their seeds counted; we also assessed the viability and photoblastic response of the seeds by using growth chambers at 25/30°C, and by a cut test on the seeds that did not germinate. Our results showed retention of viable seeds of different ages in all slices of the cephalium. Seeds were photoblastic positive with germination between 11–22% and viability above 50% in the portion of the lots that did not germinate. [ABSTRACT FROM AUTHOR]

Tomato seeds subjected to osmo-priming show fast and more uniform germination. However, osmo-priming reduces seed longevity, which is a complex seed physiological attribute influenced by several mechanisms, including response to stress. Thus, to have new insights as to why osmo-primed tomato seeds show a short life span, we performed a transcript analysis during their priming. For that, we performed gene expression studies of the heat-shock protein family genes that were previously reported to be associated with the enhancement of longevity in primed tomato seeds. Physiological assays of germination, vigour and longevity tests were used to support the data. The results show that the short life span of osmo-primed tomato seeds is related to the decrease in the expression of transcripts associated with response to stress during the priming treatment. These results are important because they add information regarding which seed longevity mechanisms are impacted by the priming treatment. In parallel, it will allow the use of these genes as markers to monitor longevity in osmo-primed tomato seeds. [ABSTRACT FROM AUTHOR]

Fire is a frequent disturbance in the Cerrado and is one of the major factors affecting vegetation structure and diversity. Fire events open gaps within the herbaceous layer and increase temperature fluctuation in the soil surface. In addition to being an important environmental filter for germination, fire is a germination cue for species with physiological dormancy. This study aimed to evaluate the germination of native grasses, using daily temperature fluctuations and heat shock to overcome physiological dormancy in native grasses. We also evaluated seed longevity after dispersal for some species. We conducted the daily temperature fluctuation experiments on seeds of ten native grass species, which were collected and then placed in germination chambers simulating thermal fluctuation throughout the day (19–55°C). We also subjected seeds to different heat-shock treatments: 100°C for 1 min, 100°C for 3 min and 200°C for 1 min. To determine seed longevity, we stored seeds for 6 and 12 months after collection and then set them to germinate (27°C, 12/12 h light). Non-germinated seeds from all experiments were tested for viability. Most species had low longevity and germination percentages. Those that had physiological dormancy were stimulated to germinate when exposed to temperature fluctuations. One species resisted temperatures up to 200°C. For all other species, neither treatment affected germination percentages. Our results indicate the importance of these environmental filters for seedling recruitment of these species, considering the low longevity and the presence of physiological dormancy. [ABSTRACT FROM AUTHOR]

Characterizing non-lethal damage within dry seeds may allow us to detect early signs of ageing and accurately predict longevity. We compared RNA degradation and viability loss in seeds exposed to stressful conditions to quantify relationships between degradation rates and stress intensity or duration. We subjected recently harvested ('fresh') 'Williams 82' soya bean seeds to moisture, temperature and oxidative stresses, and measured time to 50% viability (P50) and rate of RNA degradation, the former using standard germination assays and the latter using RNA Integrity Number (RIN). RIN values from fresh seeds were also compared with those from accessions of the same cultivar harvested in the 1980s and 1990s and stored in the refrigerator (5°C), freezer (−18°C) or in vapour above liquid nitrogen (−176°C). Rates of viability loss (P50−1) and RNA degradation (RIN⋅d−1) were highly correlated in soya bean seeds that were exposed to a broad range of temperatures [holding relative humidity (RH) constant at about 30%]. However, the correlation weakened when fresh seeds were maintained at high RH (holding temperature constant at 35°C) or exposed to oxidizing agents. Both P50−1 and RIN⋅d−1 parameters exhibited breaks in Arrhenius behaviour near 50°C, suggesting that constrained molecular mobility regulates degradation kinetics of dry systems. We conclude that the kinetics of ageing reactions at RH near 30% can be simulated by temperatures up to 50°C and that RNA degradation can indicate ageing prior to and independent of seed death. [ABSTRACT FROM AUTHOR]

UK trees require increased conservation efforts due to sparse and fragmented populations. Ex situ conservation, including seed banking, can be used to better manage these issues. We conducted accelerated ageing tests on seeds of 22 UK native woody species, in order to assess their likely longevity and optimize their conservation in a seed bank. Germination at four ageing time points was determined to construct survival curves, and it was concluded that multiple samples within a species showed comparable responses for most species tested, except for Fraxinus excelsior. Of all species studied, one could be classified as very short-lived, four as short-lived and 17 as medium, with none exceeding the medium category. The most important finding of this manuscript is that although some taxonomic trends were observed, the results indicate the need for caution when making broad conclusions on potential seed storage life at a species, genus or family level. Longevity predictions were compared to actual performance of older collections held in long-term storage at the Millennium Seed Bank, Kew. Although most collections remain high in viability in storage after more than 20 years, for short-lived species at least, there is some indication that accelerated ageing predicts longevity in seed bank conditions. For species with reduced potential longevity, such as Fagus sylvatica and Ulmus glabra, additional storage options are recommended for long-term gene banking. [ABSTRACT FROM AUTHOR]

Because the conditions used for seed ageing studies are often conducive to changes in seed lot dormancy status, taking a neural network approach might be particularly valuable in helping to disentangle signalling pathways and to unravel cause-effect relationships between the time of death during storage and deteriorative reactions leading to seed ageing (Zinsmeister et al., 2020). But not all facilities have access to advanced technologies to enable seed quality assessment or the maintenance of seed quality through the control of seed moisture. Because more traditional seed testing methods are time-consuming and require highly skilled seed analysts, techniques that promise faster, efficient and non-destructive seed testing are under development and are in great demand by the seed sector. More traditional methods of determining seed quality remain important for many species, such as seed weight, seed width, seed thickness and seed coat colour among accessions of Bambara groundnut; seed weight showed a positive relation with germination percentage in 50 accessions (Temitope Mary Jones, Nigeria). [Extracted from the article]

Vitamin E is known to scavenge lipid peroxy radicals and has a purported role in preventing seed deterioration during storage. In our previous studies using 20 rice varieties from different variety groups, the specific ratio of vitamin E homologues rather than total vitamin E content was associated with seed longevity. To validate this result, we extended the experiment to a rice panel composed of 185 Aus (semi-wild rice) varieties. Seed longevity values were determined through storage experiments at 45°C and 10.9% seed moisture content (MC). Eight types of vitamin E homologues (α-, β-, γ- and δ-tocopherol/tocotrienol) were quantified by ultra-performance liquid chromatography. The theoretical initial viability in NED, Ki, was positively correlated with γ- and δ-tocopherols and negatively correlated with α-tocotrienol. The time for viability to fall to 50% during storage at elevated temperature and relative humidity, p50, was positively correlated with δ-tocopherol. The harvest MC was negatively correlated with all seed longevity traits. Taking this factor into account in a genome-wide association (GWA) analysis, we were able to correct false positives. A consistent major peak on chromosome 4 associated with −σ−1 was detected with a mixed linear analysis. Based on rice genome annotation and gene network ontology databases, we suggest that RNA modification, oxidation–reduction, protein–protein interactions and abscisic acid signal transduction play roles in seed longevity extension of Aus rice. Although major GWA regions were not overlapped across traits, three genetic markers, on chromosomes 1, 3 and 4, were associated with both δ-tocopherol and Ki and two markers on chromosome 1 and 8 were associated with both δ-tocopherol and p50. [ABSTRACT FROM AUTHOR]

Recent evidence points to relationships between intra-specific seed mass variation and viability loss in response to ageing stress. However, little is known about how seed quality may change temporally in response to such stress. Here we examined seed–water relations of mass-separated Rudbeckia mollis seeds to better understand physiological status among mass classes. We then evaluated seed viability and vigour changes in response to various storage conditions or post-storage vigour tests (a 41°C, 75% RH stress for up to 45 d). We found similar pre-storage physiology among mass classes. However, seeds of lower mass deteriorated up to 1.5-fold faster than heavier seeds under certain conditions. Stressing seeds after storage resulted in distinct vigour differences among mass classes. For example, vigour in lower mass seeds tended to decline more compared to heavier seeds following storage in a climate-controlled room. Alternatively, vigour loss varied among mass classes following storage in a non-climate-controlled shed. Our results highlight the importance of distinguishing between pre-sowing storage and post-storage vigour effects when quantifying relative levels of viability loss among seeds of different mass. Furthermore, differential responses to storage and ageing stress among mass classes may have important implications for post-storage regeneration and subsequent population dynamics. [ABSTRACT FROM AUTHOR]

The prediction of seed longevity (P50) is traditionally performed by the use of the Probit model. However, due to the fact that the survival data are of binary origin (0,1), the fit of the model can be compromised by the non-normality of the residues. Consequently, this leads to prediction losses, despite the data being partially smoothed by Probit and Logit models. A possibility to reduce the effect of non-normality of the data would be to apply the principles of the central limit theorem, which states that non-normal residues tend to be normal as the n sample is increased. The Logit and Probit models differ in their normal and logistic distribution. Therefore, we developed a new estimation procedure by using a small increase of the n sample and tested it in the Probit and Logit functions to improve the prediction of P50. The results showed that the calculation of P50 by increasing the n samples from 4 to 6 replicates improved the index of correctness of the prediction. The Logit model presented better performance when compared with the Probit model, indicating that the estimation of P50 is more adequate when the adjustment of the data is performed by the Logit function. [ABSTRACT FROM AUTHOR]

Cultivated northern wild rice (NWR; Zizania palustris L.) has been bred and studied since the 1950s. One challenge facing researchers is the lack of storage options, due to the seed's unorthodox behaviour. This study evaluated varying storage temperature and moisture conditions for the maintenance of seed viability and dormancy breaking in Minnesota-grown NWR. First, seeds were placed in non-submerged, freezing storage (NSFS) for 12–26 weeks, then in submerged, cold storage (SCS) for 2 weeks. The addition of SCS increased germination (%G) relative to NSFS alone (<0.1% NSFS, 15% NSFS and SCS), indicating that NSFS does not kill seeds but also does not break seed dormancy. Next, the required length of SCS was evaluated by placing seeds in NSFS for 12 weeks and then in SCS for 2–14 weeks. A longer SCS period increased %G from 3 to 79%, at 2 and 14 weeks of SCS, respectively. Lastly, seeds were placed in NSFS, followed by SCS, at varying intervals over a 29-week period. Across lines, germination increased from 20 to 76% between 4 and 7 weeks of SCS, respectively, then plateaued. The results of this study indicate that NSFS could be used to store NWR seeds, but at least 7 weeks in SCS is required to overcome dormancy. Additionally, while NSFS did not break seed dormancy, physiological changes related to stratification processes were occurring in non-submerged, freezing conditions. Results also suggest that the genotypic variation in NWR could be utilized for selection to improve germination and storage viability. [ABSTRACT FROM AUTHOR]

Future climate change predictions indicate that there will be an increase in ambient air temperature. Increases in ambient air temperature will result in a corresponding increase in soil temperature. The consequences of further increases in soil temperature will potentially be detrimental for the soil seed bank of plants in terms of length of dormancy and viability of seeds. This experiment investigated the effect of different exposure temperatures and duration of exposure on the germination of semi-aquatic plant species. Seeds of four species (Alternanthera denticulata, Juncus usitatus, Persicaria lapathifolia and Persicaria prostrata) were exposed to temperatures ranging from 25 to 100°C for durations between 1 and 14 days, before being germinated in an incubator for 6 weeks. Germination occurred in all four species after exposure to temperatures ranging from 25 to 60°C. These temperatures appeared to promote germination as the temperature and duration of exposure increased. However, in P. lapathifolia and P. prostrata, the number of seeds germinating declined when exposed to 70°C and there was no germination for temperatures exceeding this. In contrast, A. denticulata and J. usitatus only began to decline when exposed to 80°C, with no germination at higher temperatures. These results suggest that soil temperatures exceeding potential threshold temperatures of 70 and 80°C will result in a decline in the number of seeds germinating and may potentially see a change in species distributions. As such soil temperatures are already being experienced throughout Australia, some species may already be close to their thermal threshold. [ABSTRACT FROM AUTHOR]

Seeds of 15 diverse rice accessions, representing aus , indica , temperate japonica and tropical japonica subpopulations, were produced under temperate climate conditions in Korea and used for vitamin E analysis and seed storage experiments at 45°C and 10.9% seed moisture content. High γ -tocotrienol was significantly positively correlated with seed longevity. In addition, a high β -tocopherol proportion relative to δ -tocopherol was significantly negatively correlated with seed longevity. Using high-density single-nucleotide polymorphism marker data, DNA haplotype analysis showed clear allelic variations in the region of two S-adenosylmethionine synthetase genes: LOC_Os04g42095 and LOC_Os11g15410, which regulate the conversion of δ -tocopherol into β -tocopherol. Four indica accessions with rare and subpopulation-specific alleles showed a 2.3-fold lower β -/ δ -tocopherol ratio compared with accessions from other subpopulations. [ABSTRACT FROM AUTHOR]

We studied the variability of germination, dormancy and viability loss of Hirschfeldia incana seeds in relation to seed size. Seeds were stored at 35°C under humid [75% relative humidity (RH)] or dry (33% RH) conditions. Seed germination and electrolyte leakage were evaluated periodically. Small seeds had lower longevity at humid or dry storage conditions (5 or 407 days, respectively) than large or intermediate seeds (7–9 or 536–727 days, respectively). Moreover, H. incana shows variability in seed dormancy related to seed size within a population, with small seeds having lower dormancy (13%) than intermediate (50%) or large seeds (72%). Dormancy was partially released after a short storage at 35°C and humid conditions. Under dry storage conditions, endogenous dormancy cycles were observed for over a year, and longer times of storage had a dormancy-breaking effect through dry after-ripening. Results suggest a dual strategy producing non-dormant seeds with low longevity that will germinate immediately after dispersal, and seeds with greater longevity that will delay germination. Membrane permeability increased linearly with ageing at both humid and dry storage (R 2 = 0.60). Small seeds showed greater conductivity than intermediate or large seeds (0.7, 0.4 or 0.3 mS g–1 dry weight, respectively, at the 80% germination). The conductivity test could be used to evaluate the quality of H. incana seeds and would allow us to identify dormant (non-germinating) seed lots as viable. However, the influence of storage conditions and variability within a seed population on seed longevity should be taken into account when evaluating seed quality. [ABSTRACT FROM AUTHOR]

The genus Aegilops belongs to the secondary gene pool of wheat and has great importance for wheat cultivar improvement. As a genus with only annual species, regeneration from seeds in Aegilops is crucial. In several species in Aegilops , spikes produce different seed morphs, both in size and germination patterns. However, little is known about the ecology of seed germination, nor about the seed longevity in this genus. Here we investigated the germination phenology of Ae. neglecta under laboratory and field conditions and assessed longevity of different seed morphs of five additional Aegilops species using controlled ageing tests. Large seeds were short-lived and germinated faster than small seeds in most of the species. Field experiments with Ae. neglecta showed that large seeds of the dimorphic pair germinated 3 months after dispersal in contrast to 14 months for smaller seeds. Differences in longevity were detected not only in dimorphic seed pairs, but also among seeds from different positions on the spike. Our results indicate that different longevities in seed morphs of Aegilops may reflect a different soil seed bank persistence, with smaller seeds able to maintain a higher viability after dispersal than larger ones, thereby spreading seedling emergence over two years. Differences of seed germination and longevities between seed morphs in Aegilops may have important implications for ex situ seed conservation and reinforce the hypothesis of a bet-hedging strategy in the germination ecology of this genus. [ABSTRACT FROM AUTHOR]

Seed longevity is influenced by many factors, a widely discussed one of which is the seed lipid content and fatty acid composition. Here, linear and non-linear regressions based on machine learning were applied to analyse germinability and seed composition of a set of 42 oilseed rape (Brassica napus L.) accessions grown under the same single environment and at the same time following a period of up to 31 years storage at 7°C. Mean viability was halved after 27.0 years of storage, but this figure concealed a major influence of genotype. There was also wide variation with respect to fatty acid composition, particularly with respect to oleic, α-linolenic, eicosenoic and erucic acid. Linear regression (r L) revealed significant correlation coefficients between normal seedling appearance and the content of α-linolenic acid (+0.52) and total oil (+0.59). Multivariate regression using artificial neural networks including a radial basis function (RBF), a multilayer perceptron (MLP) and a partial least square (PLS) recognized underlying structures and revealed high significant correlation coefficients (r M) for oil content (+0.87), eicosenoic acid (+0.75), stearic acid (+0.73) and lignoceric acid (+0.97). Oil content or a combination of oleic, α-linolenic, arachidic, eicosenoic and eicosadienoic acids and glucosinolates resulted in highest model fitting parameters R 2 of 0.90 and 0.88, respectively. In addition, the glucosinolate content, predominantly in the Brassicaceae family and ranging from 4.6 to 79.5 µM, was negatively correlated with viability (r L = ‒0.43). Summarizing, oil content, some fatty acids and glucosinolates contribute to variations in average half-life (15.2 to 50.7 years) of oilseed rape seeds. In contrast to linear regression, multivariate regression using artificial neural networks revealed high associations for combinations of parameters including underestimated minor fatty acids such as arachidic, stearic and eicosadienoic acids. This indicates that genetic and seed composition factors contribute to seed longevity. In addition, multivariate regressions might be a successful approach to predict seed viability based on fatty acids and seed oil content. [ABSTRACT FROM AUTHOR]

Drying reduces seed moisture content, which improves subsequent seed survival periods. Diverse maximum temperatures have been recommended to limit or avoid damage to seeds, but some high-temperature drying regimes may improve subsequent seed quality. Seeds from 20 different accessions of five rice (Oryza sativa L.) variety groups (aromatic, Aus, Indica, temperate Japonica, tropical Japonica) were harvested over several seasons at different stages of maturation and either dried throughout at 15°C/15% relative humidity (RH) or for different initial periods (continuous or intermittent) in different drying regimes at 45°C before final equilibrium drying at 15°C/15% RH. Subsequent seed longevity in hermetic storage at 45°C with 10.9% moisture content was determined. In no case did initial drying at 45°C provide poorer longevity than drying at 15°C/15% RH throughout. There was a split-line relation, which did not differ amongst investigations, between longevity after initial drying at 45°C relative to that at 15°C/15% RH throughout and harvest moisture content, with a break point at 16.5% (a seed moisture status of about –14 MPa). Below 16.5%, relative longevity did not differ with harvest moisture content with little or no advantage to longevity from drying at 45°C. Above 16.5%, relative longevity showed a positive relation with harvest moisture content, with substantial benefit from drying at 45°C to subsequent longevity of seeds harvested whilst still moist. Hence, there are temporal (immediately ex planta cf. subsequent air-dried storage) and water status discontinuities (above cf. below 16.5%) in the effect of temperature on subsequent air-dried seed longevity. [ABSTRACT FROM AUTHOR]

Conserving alpine ecosystems and the plant communities they contain using ex situ conservation requires an understanding of seed longevity. Knowledge of seed longevity may determine the effectiveness of ex situ seed banking for alpine plant conservation, and may provide insight into plant recruitment in situ. We sought to determine the influence of elevation and climatic variables, as well as plant and seed traits, on the seed longevity of 57 species inhabiting a unique biome, (sub-)alpine regions of mainland Australia. Seed longevity was estimated using controlled accelerated ageing tests to determine the time taken for seed viability to fall by 50%. We found that, across the study species, like alpine seeds elsewhere in the world, Australian alpine seeds are relatively short-lived and overall shorter-lived than Australian plants in general. Seed mass and elevation explained most of the variation in seed longevity among the Australian alpine species considered. Species with larger seed mass, and collections made at higher elevations, were found to have relatively short-lived seeds. Phylogeny, however, explained very little of the variation in longevity. Our results suggest that viability testing for Australian alpine seeds in ex situ seed banks should be conducted with shorter intervals than for the non-alpine flora. This study highlights how seed longevity in the Australian Alps is not dictated primarily by evolutionary lineage but rather by a complex combination of environmental variables and intrinsic seed characteristics. Potential implications for conservation ex situ and in situ in the context of climate change are discussed. [ABSTRACT FROM AUTHOR]

Ultra-dry storage, storing orthodox seeds at ambient temperatures with moisture contents below 5%, can maintain seed viability for long periods with low input. Optimum moisture contents for ultra-dry storage exist and vary substantially among different seed lots due to their differences in desiccation tolerance, which is associated with the accumulation of protective compounds. To study the relationship between moisture contents of ultra-dry stored species, seed composition and the free-radical scavenging activity (FRSA). Eleven seed lots of maize, wheat, pepper, peanut, Chinese cabbage, and cucumber were chosen and multiple stepwise regression analysis was applied. In general, analysis of the seed lots revealed that optimum moisture contents for highest seed viability are below equilibrium moisture at 13% relative humidity and 20°C. Nevertheless, seed composition differed significantly among species. Lipids, flavonoids and the FRSA were significantly negatively correlated with the optimum moisture content of ultra-dry stored whole seeds and accounted for 97.7% of the total variation in the optimum moisture content. Lipids had the highest effect (90.0%) on the optimum moisture content of ultra-dry storage, which is consistent with the previous results. The FRSA and flavonoids accounted for 4.8 and 2.9% of total variation of optimum moisture content of ultra-dry stored whole seeds, respectively. The FRSA and flavonoids were also significantly negatively correlated with the optimum moisture content for non-lipid fraction of ultra-dry stored seeds, and accounted for 74.1 and 15.3% of the total variation in the optimum moisture content, respectively. [ABSTRACT FROM AUTHOR]

Post-harvest drying prolongs seed survival in air-dry storage; previous research has shown a benefit of drying moist rice seeds at temperatures greater than recommended for genebanks (5-20°C). The aim of this study was to determine whether there is a temperature limit for safely drying rice seeds, and to explore whether the benefit to longevity is caused by high-temperature stress or continued seed development. Seeds of two rice varieties were harvested at different stages of development and dried initially either over silica gel, or intermittently (8 h day-1) or continuously (24 h day-1) over MgCl2 at temperatures between 15 and 60°C for up to 3 days. Seeds dried more rapidly the warmer the temperature. Subsequent seed longevity in hermetic storage (45°C and 10.9% moisture content) was substantially improved by increase in drying temperature up to 45°C in both cultivars, and also with further increase from45 to 60°C in cv. 'Macassane'. The benefit of high-temperature drying to subsequent longevity tended to diminish the later the stage of development at seed harvest. Intermittent or continuous drying at high temperatures provided broadly similar improvements to longevity, but with the greatest improvements detected in a few treatment combinations with continuous drying. Heated-air drying of rice seeds harvested before maturity improved their subsequent storage longevity by more than that which occurred during subsequent development in planta, which may have resulted from the triggering of protection mechanisms in response to high-temperature stress. [ABSTRACT FROM AUTHOR]

Vitamin E (tocols) is a key metabolite for efficient scavenging of lipid peroxy radicals that cause membrane breakdown during seed ageing. However, in rice, this hypothesis has been tested for very few lines only and without considering intraspecific variation in genomic structure. Here, we present a correlation study between tocols and seed longevity using a diverse rice panel. Seeds of 20 rice accessions held in the International Rice Genebank at the International Rice Research Institute, representing Aus, Basmati/Sadri, Indica, temperate Japonica and tropical Japonica variety groups, were used for tocols analysis (quantification of α-, β-, γ- and δ-tocopherol/tocotrienol by ultra-performance liquid chromatography) and storage experiments at 45°C and 10.9% seed moisture content. To examine the effects of DNA-haplotype on the phenotype, the 700 K high-density single-nucleotide polymorphism marker dataset was utilized. Both seed longevity (time for viability to fall to 50%; p50) and tocols content varied across variety groups related to the heterogeneity in the genetic architecture. Among eight types of tocol homologues, α-tocopherol and γ-tocotrienol were significantly correlated with p50 (negatively and positively, respectively). While temperate Japonica varieties were most abundant in α-tocopherol, Indica varieties recorded 1.3- to 1.7-fold higher γ-tocotrienol than those of other groups. We conclude that the specific ratio of tocol homologues rather than total tocols content plays an important role in the seed longevity mechanism. [ABSTRACT FROM AUTHOR]

The conservation of this tree is therefore important for the conservation of this primate. The Western Ghats of India are recognized as a biodiversity hotspot and are remarkable for their floristic diversity and endemism. [Extracted from the article]

Seed quality is of great importance in optimizing the cost of crop establishment. Rapid and non-destructive seed quality detection methods must therefore be developed for agriculture and the seed production industry. This review focuses primarily on non-destructive techniques, namely machine vision, spectroscopy, hyperspectral imaging, soft X-ray imaging, thermal imaging and electronic nose techniques, for assessing the quality of agricultural seeds. The fundamentals of these techniques are introduced. Seed quality, including chemical composition, variety identification and classification, insect damage and disease assessment as well as seed viability and germinability of various seeds are discussed. We conclude that non-destructive techniques are accurate detection methods with great potential for seed quality assessment. [ABSTRACT FROM PUBLISHER]

Water availability regulates timing of germination, especially in those environments where it is a limiting factor. However, the water requirements for germination of most wild Mediterranean species are unknown. In this work we analysed the germination response to water stress of eight Cistaceae species with hard-coated seeds, which are typical for the Mediterranean shrublands. Seeds were exposed to a heat shock in order to overcome physical dormancy and then incubated under five water potentials (0, -0.2, -0.4, -0.6 and -0.8 MPa). Ungerminated seeds following these treatments were transferred to water in order to evaluate the recovery of germination. Additionally, at the end of the experiment, viability of still ungerminated seeds was examined. We analysed final germination percentage, time to reach 50% of the final germination (t50), recovery of germination and seed viability in relation to water stress treatments. Furthermore, hydrotime analysis was performed; sensitivity to water stress, as characterized by Ψb(50), was checked in relation to seed size of species. Overall, water stress delayed and decreased germination but species showed different germination sensitivities, which were not related to seed size. Recovery of germination was high after disappearance of water stress but seed viability decreased in some species. Consequently, post-fire germination of Cistaceae must be strongly regulated by water availability and their seeds can recover germination capacity when sufficient water is available after long periods of incomplete hydration. However, some seeds die during the wait. [ABSTRACT FROM AUTHOR]

Does seed dormancy allow disturbance-oriented forest herbs such as Ageratina altissima to persist in heterogeneous natural communities? To document seed longevity and dormancy state, Ageratina seeds were buried in nylon mesh bags in second-growth forest stands in south-eastern Ohio, USA. Bags were recovered at 2-month intervals, and seeds were tested for viability and germinability in the lab. Live seed numbers declined rapidly, with seed banks exhausted in an estimated 33-37 months. Seeds showed a strong dormancy polymorphism, with 71-84% of live seeds germinable between March and July, the season of natural seedling emergence. At other dates, most seeds appeared to be in a state of induced dormancy, allowing little (0-21%) germination. The slope aspect of the burial site, an important factor controlling aboveground vegetation, had no effect on seed longevity or dormancy condition. Dormancy in Ageratina appears to be adapted to allow opportunistic germination in late spring-early summer, but to prevent germination in less benign periods. Seed longevity is shorter than the natural frequency of gaps in mesophytic forest. We conclude that a long-term dispersal/dormancy trade-off is probably an oversimplification of the spatial ecology of this species. The primary function of dormancy appears to be short-term tracking of seasonal variation. [ABSTRACT FROM AUTHOR]

Light and fluctuating temperatures are two important factors triggering seed germination. The aim of this work was to: (1) elucidate the effect of temperature, light regime and storage time on seed germination in nine taxa of Verbascum spp., collected from different habitats in the Mediterranean area; and (2) estimate threshold temperatures for seed germination. For all taxa, germination assays were performed at constant and fluctuating temperatures, both in continuous darkness (D) and in alternating light/dark (L/D; 12 h photoperiod). Final germinated proportions (FGPs), base (Tb), optimal (To) and cut-off (Tc) temperatures were derived. At constant temperatures, seed germination was strongly suppressed under the D regime. In L/D, the effect of storage time was very small and the highest FGPs were observed from 15 to 30°C (40–100%), depending on the species. Tb ranged from below 7 to above 10°C and it appeared to be constant within each seed lot. To and Tc showed some within-lot variability and were higher for fast-germinating seeds in each lot. Considering fluctuating temperatures, germination appeared to be quicker and more complete than at constant temperatures. The germination of Verbascum spp. is favoured in L/D and fluctuating temperatures, which explains their pioneer character when positioned near the soil surface and under a low vegetation canopy. V. arcturus and V. pinnatifidum were shown to be less favoured by L and fluctuating temperatures, which might explain their ability to germinate in rocky areas or sandy dunes, even when they are not directly exposed to the light. [ABSTRACT FROM AUTHOR]

Poor wheat seed quality in temperate regions is often ascribed to wet production environments. We investigated the possible effect of simulated rain during seed development and maturation on seed longevity in wheat (Triticum aestivum L.) cv. Tybalt grown in the field (2008, 2009) or a polythene tunnel house (2010). To mimic rain, the seed crops were wetted from above with the equivalent of 30 mm (2008, 2009) or 25 mm rainfall (2010) at different stages of seed development and maturation (17–58 DAA, days after 50% anthesis), samples were harvested serially, and subsequent air-dry seed longevity estimated. No pre-harvest sprouting occurred. Seed longevity (p50, 50% survival period in experimental hermetic storage at 40°C with c. 15% moisture content) in field-grown controls increased during seed development and maturation, attaining maxima at 37 (2008) or 44 DAA (2009); it declined thereafter. Immediate effects of simulated rain at 17–58 DAA in field studies (2008, 2009) on subsequent seed longevity were negative but small, e.g. a 1–4 d delay in seed quality improvement for treatments early in development, but with no damage detected at final harvests. In rainfall-protected conditions (2010), simulated rain close to harvest maturity (55–56 DAA) reduced longevity immediately and substantially, with greater damage from two sequential days of wetting than one; again, later harvests provided evidence of recovery in subsequent longevity. In the absence of pre-harvest sprouting, the potentially deleterious effects of rainfall to wheat seed crops on subsequent seed longevity may be reversible in full or in part. [ABSTRACT FROM AUTHOR]

New trends in crop breeding include analytical approaches to identify metabolic fingerprints that can be used for associations to the genetic background. The biochemical phenotype, as a result of plant endogenous factors and interaction with the environment, has the potential to increase the accuracy of forecasting regarding agronomical quality factors. In this study a metabolite profile analysis by gas chromatography–mass spectrometry (GC–MS) was conducted on sets of seed material from sugar beet. One set represented high-performing varieties with a close genetic background and with a similar quality in terms of germination capacity. The second set contained seed lots from different genotypes comprising different germination capacities. By multivariate statistical analyses high variance in both sample sets was revealed. These data were further allocated to corresponding metabolite classes. It could be shown that an untargeted GC–MS approach has the power to resolve differences in the molecular phenotypes of related offspring lines. Metabolic profiles were found to correlate more to genotypic differences than to differences in the germination capacity. [ABSTRACT FROM AUTHOR]

Orchid seeds are among the smallest seeds in nature and they are naturally rich in fatty acids. However, the fatty acid composition of orchid seeds has not been investigated because the sample masses utilized for widely used methods for fatty acid profiling would generally require prohibitively large numbers (i.e. 10,000s) of seeds. The present work aimed to develop a method for fatty acid analysis using gas chromatography–mass spectrometry on small quantities (mg) of seeds. The method was developed using the seeds of two species, Dactylorhiza fuchsii, a temperate terrestrial, and Grammatophyllum speciosum, a tropical epiphyte. A range of sample masses was tested to determine the minimum mass required to achieve reliable fatty acid composition data. A direct transesterification method was used, which did not require extraction of fatty acids from seeds prior to analysis, and the effects of seed processing (crushed versus intact seeds) and incubation time in toluene on fatty acid yield were tested. Stable fatty acid profiles were obtained using as little as 10 mg of seeds. Neither crushing the seeds nor extending the toluene incubation step had much effect on the fatty acid yield. The simple direct transesterification method presented will enable the fatty acid composition of orchid seeds, and possibly other small seeds, to be determined reliably for studies into seed development, storage and germination. [ABSTRACT FROM AUTHOR]

Miconia chartacea is a widely distributed tree in Brazil, occurring at altitudes ranging from 300 m to 1900 m in the Caatinga, Cerrado and Atlantic Forest biomes. In this work we attempted to classify M. chartacea seeds regarding their behaviour during storage and their germination syndrome and to determine, from a storage test in Cerrado soil and laboratory conditions in situ and ex situ, the longevity of seeds, as well as the capacity of the species to form a soil seed bank. The results suggested that M. chartacea seeds form a transient soil seed bank in the Cerrado and can be classified as orthodox in terms of storage behaviour, although the seeds are dispersed with a relatively high water content. The life span of seeds was favoured in soil-stored seeds in comparison with dry storage at 25°C, whereas storage at low temperatures prevented a decrease of the seed's germinability with storage time (330 d). M. chartacea seeds are dispersed during the dry season and germinate during the next rainy season, which can be classified as an intermediate–dry germination syndrome. Seeds of this species are dispersed in the Cerrado when temperatures and soil moisture are relatively low, which favours the formation of a soil seed bank, considering that the seeds tolerate desiccation and their longevity is favoured by low temperatures. A transient seed bank type is favoured by the loss of viability in storage at warm temperatures linked to the rainy season, and the predictable seasonal variations in climate in the region, with germination being restricted to the beginning of the rainy season. [ABSTRACT FROM PUBLISHER]

Plant genetic resources are conserved by genebanks mainly in the form of seeds. In most of the cases, the dried seeds can be stored for a considerable period of time, but eventually seed deterioration results in the inability to generate healthy seedlings. Prolonging seed longevity during storage reduces the frequency of regeneration, which is beneficial from a genetic as well as a management point of view. To reduce the rate of deterioration, cool and dry storage conditions are usually practised for long-term seed storage. In spite of the growing body of evidence that seed deterioration is predominantly caused by oxidative processes, the importance of seed storage under anoxic conditions has received little attention from the genebank community. Herein, we report on the effects of anoxia on seed viability, the oxygen uptake by dry seeds in closed containers and the permeability for oxygen of various seed storage containers. Our results confirm that the ageing of dry seeds is accelerated by the presence of oxygen in the storage environment. Therefore, we recommend that genebanks store dry seeds under anoxic conditions to prolong their longevity during ex situ conservation. To reduce the initial rate of viability loss, we further recommend that the period of temporary storage after seed harvest be minimized and also that the seeds are kept during this period under controlled conditions, including anoxia. [ABSTRACT FROM PUBLISHER]

Seeds can synchronize their germination and dormancy cycles to regular seasonal environmental changes. The present work sought to evaluate the in-situ longevity of the buried seeds of two species of Syngonanthus and two species of Comanthera (Eriocaulaceae) in the region of natural occurrence (Serra do Cipó Range, south-eastern Brazil), and to relate their germination responses to seasonal climatic changes. Samples were exhumed bimonthly and germination was tested under a 12-h photoperiod (30 μmol m− 2s− 1) at optimal germination temperature. The seeds of Comanthera showed high deterioration after the first year of burial, especially C. elegans, which reflects their incapacity to form viable soil seed banks. The buried seeds of C. bisulcata, S. anthemidiflorus and S. verticillatus acquired secondary dormancy during the rainy season (spring/summer, higher temperatures) which was alleviated during the subsequent dry season (autumn/winter, lower temperatures). It is concluded that C. bisulcata, S. anthemidiflorus, and S. verticillatus form seed banks of the persistent type and demonstrate consecutive cycles of germination/dormancy, accompanying annual seasonal changes for at least 2 years. [ABSTRACT FROM AUTHOR]

The seasonality of the Mediterranean climate has important implications for plant physiology and some specific conditions must be met before germination can occur. Most plants sprout during the spring season although a few germinate during the autumnal rainy period. To understand the patterns of germination under autumn conditions we selected five Mediterranean autumn-flowering geophytes that usually co-exist in fire-prone habitats: Leucojum autumnale, Narcissus cavanillesii, Narcissus serotinus, Scilla autumnalis and Urginea maritima. Experiments were performed under conditions simulating those prevailing in the habitat during the autumnal Mediterranean season when seeds of these species usually germinate. In all species, germination occurred quickly ( < 7 d), was usually higher at the lowest temperatures tested (15°C, 20°C; >89%) and no signs of delayed germination were detected. Nevertheless, species usually had different patterns of seed germination, a strategy that might avoid interspecific competition when co-occurring in the same habitats. Germination was lower and slower in light than in darkness, suggesting that under natural conditions germination of seeds directly exposed to sunlight can be severely restricted. Several fire-dependent treatments (heat and ash) revealed a lack of fire-stimulated germination, and treatments even had a negative effect. In addition, only a small fraction of seeds remained viable after 1 year of dry lab storage and their germinability was very low, suggesting the absence of a permanent soil seed bank in the life cycle of these geophyes. [ABSTRACT FROM PUBLISHER]

Pollinator visits to flowers of self-incompatible tropical trees are critical for plant fecundity. However, few studies have examined how much of the variance in tropical tree fecundity is explained by individual attributes of trees (e.g. number of flowers), and how much is due to contextual variables such as distances to nearest flowering neighbours. Using multiple regressions we examined the relative contributions of these factors to the pollination and fecundity of Goetzea elegans, a mainly self-incompatible tree endemic to Puerto Rico. We studied the largest wild population of the species during the peak flowering and collected data on the frequency of pollinator visits (N = 25 trees), and the fecundity of the whole population (N = 105), including the visitation rate of two pollinators (the honey bee Apis mellifera and the bananaquit Coereba flaveola), the total number of flowers produced by each tree, and the total fruit set and seed viability per tree. We also recorded the distance to flowering conspecifics and heterospecifics, and the height for each tree. Flower number had a strong positive effect on pollinator visitation, but distance to nearest neighbours was equally or more important than flower number in influencing fecundity. Also, competition for limited pollinators between G. elegans and other species has a stronger effect than the facilitation that conspecifics may provide. Our results suggest that pollinator visits and aspects of fecundity of G. elegans depend both on the attributes of individual plants, and on those of the community of other nearby plants. [ABSTRACT FROM PUBLISHER]

The tropical montane conifer tree Widdringtonia whytei is found in small fragments on Mulanje Mountain in Malawi. A study was conducted with the objectives of determining the effect of population size, tree stem diameter and crown position on the proportion of viable seeds per cone produced by W. whytei at three sites (Sombani, Chambe and Lichenya) on Mulanje Mountain. Three population sizes, namely small (fragments with ≤10 cone-bearing trees), medium (fragments with 11–20 cone-bearing trees) and large (fragments with >20 cone-bearing trees) and isolated trees were sampled at each study site. In each fragment, four cone-bearing trees were randomly located, 20 mature cones were collected from each tree and the viability of seeds was tested. Only 23% of the seeds per cone were viable but seed viability per cone was highly variable among fragments. Large fragment populations produced the highest proportion of viable seeds per cone (30%), followed by similar proportions in small fragments (28.3%) and isolated trees (26.1%), with the lowest proportions in medium-sized fragments (18.7%), indicating a non-linear relationship between viable seed output per cone and population size. Tree stem diameter and crown position had no effect on the proportion of viable seeds per cone. Further studies are needed to identify the factors that lead to the low viable seed output per cone, and how this influences whole-tree seed production in W. whytei. [ABSTRACT FROM PUBLISHER]

Lettuce (Lactuca sativa L.) and onion (Allium cepa L.) seeds have relatively short longevity during storage and their germination is sensitive to environmental stress. Seed priming (controlled hydration followed by drying) can improve seed germination under stressful conditions, inducing faster and more uniform germination over broader temperature ranges, but it can also reduce seed longevity in storage. Controlled deterioration (CD) tests are often employed to study longevity by ageing seeds rapidly at elevated temperature and moisture content, and primed seeds are particularly sensitive to CD conditions. As reactive oxygen (O2) species are thought to be involved in seed deterioration, we tested whether storage under reduced O2 atmospheres (0 and 2% O2) would extend the longevity of primed and non-primed seeds under low relative humidity (RH) (33% RH+37°C) and CD (75% RH+50°C) storage conditions. The longevity of both non-primed and primed lettuce seeds in low RH storage was extended by anaerobic environments, but the effect of O2 was much less under CD conditions. In onion, only primed seeds exhibited a beneficial effect of low O2 atmospheres under both types of ageing conditions. In both species, storage under anaerobic conditions was beneficial for extending the longevity of primed seeds, but was not able to ameliorate fully the negative effect of priming on storage life. [ABSTRACT FROM PUBLISHER]

Dehydrins are late embryogenesis abundant (LEA) proteins that accumulate during seed maturation and in response to abiotic stresses in vegetative tissues. They are thought to protect cellular components from dehydration stress. However, whether they play a role in survival in the dry state is not clear. In this study, an RNA interference (RNAi)-construct against the seed-expressed dehydrin of Arabidopsis thaliana, LEA14 (At2g21490), was introduced to wild-type plants, which led to a strong reduction in transcript abundance of the target gene as well as that of two other seed-expressed dehydrin homologues, XERO1 (At3g50980) and RAB18 (responsive to abscisic acid 18, At5g66400) in the transformants. Mature, dry seeds from the RNAi plants germinated to at least 95% after rehydration, indicating that seed desiccation tolerance was not affected, while they exhibited a twofold reduction in longevity. When stored at 75% relative humidity and 35°C, the seeds of two independent RNAi lines lost 50% of their viability in 10 d and 5 d, respectively, while it took 17 d for wild-type seeds to lose 50% viability. In addition, when seeds were imbibed in the presence of 100 mM NaCl, the seeds of RNAi plants exhibited reduced germination compared to wild-type seeds, suggesting that at least one of the three seed-specific dehydrins plays a role both against deterioration during storage at low moisture content and when imbibed tissues are submitted to salt stress at high moisture. [ABSTRACT FROM PUBLISHER]

Although oilseed rape has become one of the most important oil crops in Europe, little is known regarding the viability of its seed under conditions of long-term storage. We report here an examination of oilseed rape seed longevity performed on a set of 42 accessions housed at the German ex situ genebank at IPK, Gatersleben. A comparison of germination between the accessions stored for 26 years showed that viability was in part genetically determined, since it ranged between 42 and 98%. An attempt was made to define the genetic basis of viability by subjecting a mapping population of doubled haploids to three artificial ageing treatments. Quantitative trait loci (QTL) were detected on six chromosomes: N6, N7, N8, N15, N16 and N18. The chromosomal locations of these QTL were compared with their syntenic regions in Arabidopsis thaliana in order to explore what genes might underlie genetic variation for longevity. [ABSTRACT FROM AUTHOR]

Pre-harvest sprouting (PHS) is a serious risk when adapting quinoa (Chenopodium quinoa) seed production to different temperate environments. Two quinoa accessions, ‘2-Want’ and ‘Chadmo’ were evaluated under field conditions in the Argentinean pampas over 2 years on five different sowing dates, to explore a range of climate conditions under which seed filling is manageable in this region. Both accessions exhibited dormancy during seed development and maturation under the conditions examined; however, dormancy expression was restricted to low temperatures in 2-Want, while seeds of Chadmo, originating from the humid island of Chiloe, southern Chile, expressed a high level of dormancy at all examined temperatures. Dormancy release was observed as a reduction in the lowest temperature permissible for seed germination, which broadened the optimal germination temperature window. Higher storage temperature increased the rate of dormancy release. The environment during seed development on the mother plant affected the levels and patterns of seed dormancy, with higher temperatures and longer photoperiods promoting dormancy. As dormancy was released before the next production period, the levels of dormancy observed in the accession would allow timely planting and uniform germination, while dormancy during seed maturation ensures the prevention of PHS. Chadmo showed deeper dormancy levels in all situations, compared with 2-Want, therefore greater PHS tolerance under various conditions in the pampas region can be expected for Chadmo, which makes this accession a better candidate to be included in adaptive breeding programmes for quinoa. [ABSTRACT FROM PUBLISHER]

Restoration of semi-natural grassland communities involves a combination of (1) sward disturbance to create a temporal window for establishment, and (2) target species introduction, the latter usually by seed sowing. With great regularity, particular species establish only poorly. More reliable establishment could improve outcome of restoration projects and increase cost-effectiveness. We investigated the abiotic germination niche of ten poorly establishing calcareous grassland species by simultaneously exploring the effects of moisture and light availability and temperature fluctuation on percentage germination and speed of germination. We also investigated the effects of three different pre-treatments used to enhance seed germination – cold-stratification, osmotic priming and priming in combination with gibberellic acid (GA3) – and how these affected abiotic germination niches. Species varied markedly in width of abiotic germination niche, ranging from Carex flacca with very strict abiotic requirements, to several species reliably germinating across the whole range of abiotic conditions. Our results suggest pronounced differences between species in gap requirements for establishment. Germination was improved in most species by at least one pre-treatment. Evidence for positive effects of adding GA3 to seed priming solutions was limited. In several species, pre-treated seeds germinated under a wider range of abiotic conditions than untreated seeds. Improved knowledge of species-specific germination niches and the effects of seed pre-treatments may help to improve species establishment by sowing, and to identify species for which sowing at a later stage of restoration or introduction as small plants may represent a more viable strategy. [ABSTRACT FROM PUBLISHER]

The transition from the dormant to the non-dormant state of a viable and mature seed can take place at low hydration by exposure to air-dry storage conditions (dry afterripening; AR). The events occurring during this loss of dormancy are of considerable physiological, ecological and agricultural interest. AR may be attributable to increased sensitivity to germination-stimulating factors and a widening of the temperature window for germination. Genetic, –omics and physiological studies on this mode of dormancy breaking provide support for a key role of the balance between gibberellin (GA) and abscisic acid (ABA) metabolism and sensitivity. Recent evidence also supports a possible role for ethylene (ET) in this complex signalling network that is necessary for AR implementation. However, hormone-independent signals, such as reactive oxygen species (ROS), nitrate (NO _{3}^{ - } ) or nicotinamide adenine dinucleotide (NAD+), also appear to be involved. The way in which hormone- and non-hormone-signalling pathways affects each other (cross-talk) is still under study. This review provides updated information on the programmes that overcome seed dormancy. Thus, we have reviewed: (1) the –omic status in dry seeds; (2) the relationship between temperature and nitrate signalling and AR; (3) alterations in ABA/GA synthesis and signalling; (4) the action of hormone molecules other than ABA and GA (i.e. ET, salicylic and jasmonic acids); and (5) participation of reactive oxygen species (ROS), NAD+ and protein carbonylation. Taken together, the acquisition and implementation of dry AR involve a complex signalling network that is difficult to disentangle. [ABSTRACT FROM PUBLISHER]

Seed dormancy and germination involve the concerted operation of molecular and biochemical programmes. It has become feasible to study these processes in great detail, using the current methods for transcriptome, proteome and metabolome analysis. Yet, the large amounts of data generated by these methods are often dazzling and demand efficient tools for data visualization. We have used the freely available PageMan/MapMan package (http://MapMan.gabipd.org) to visualize transcriptome and metabolome changes in Arabidopsis thaliana seeds during dormancy and germination. Using this package we developed two seed-specific MapMan pathways, which efficiently capture the most important molecular processes in seeds. The results demonstrated the usefulness of the PageMan/MapMan package for seed research. [ABSTRACT FROM PUBLISHER]