Dry-stored Seeds Research Articles

Seed dormancy-break and germination of Cynanchum forrestii (Asclepiadaceae), an endemic medicinal species of southwest China

Cynanchum forrestii is an over-harvested medicinal plant species in China. At present, wild resources of this species urgently need to be conserved and cultivated to meet the demand of the pharmaceutical industry. However, information on reproduction and propagation is not available. Here, different treatments were assessed to develop an effective protocol for facilitating seed germination of this species. Once seeds were released from physiological dormancy, using 25/15°C with a 12-hour light period promoted germination. Seeds cold stratified at 4°C for 90 days and 120 days germinated to 87 and 91%, respectively, and mean germination time was 11.53 and 10.52 days, respectively. The combination of 60 days cold stratification and 200 mg L-1 GA3 significantly increased germination from 11% (fresh seeds) to 87%. Among four concentrations used, 200 mg L -1 GA3 was the most effective for promoting germination of 90-day dry-stored seeds. Taken together, cold stratification for 90 days or more is recommended as a practical measure to break innate dormancy of this species.

Dry storage alters intraspecific variation in phenotypic traits at early life stages: evidence from a dominant alpine meadow species

AbstractThe intraspecific variations of phenotypic traits in the early life stages, such as seed germination and seedling establishment, are important components affecting species adaptation and differentiation. As one of the most common ways in which seeds are maintained, dry storage usually affects these traits, by either increasing or decreasing variation among populations. However, little is known about how the interaction between dry storage and population variation of a species affects the performance and adaptability of early life-cycle traits. In this study, we conducted experiments with seeds from ten populations of Elymus nutans along an altitudinal gradient on the eastern Qinghai-Tibet Plateau. Fresh seeds and seeds stored dry for 6 months were used to quantify the temperature thresholds for germination, determine seedling emergence and survival in two common gardens and examine the correlation between these traits and environmental conditions of population provenance. Dry storage increased germination percentage, germination speed and seedling emergence, and decreased intraspecific variation in germination traits of seeds (reduced by 33.36, 52.05 and 20.45% for Tb, θT(50) and σθT, respectively). Dry storage had little effect on the intraspecific variation of seedling emergence and survival. In addition, the temperature threshold for germination cannot be used to predict seedling emergence and survival in either common garden, regardless of whether seeds were stored or not. These results indicated that it is feasible to use dry-stored seeds to evaluate and select suitable provenances in ecological restoration, and using dry-stored seeds in ecological restoration projects is expected to achieve better vegetation restoration results than fresh seeds. On the other hand, the status of seeds (fresh vs. dry stored) should be considered in an evaluation of the adaptive value of plant functional traits, especially in the early life stages, otherwise, inconsistent conclusions may be drawn.

Dry-storage and light exposure reduce dormancy of Arabian desert legumes more than temperature

Propagation and conservation of desert plants are assisted by improved understanding of seed germination ecology. The effects of dry-storage on dormancy and germination were studied in seven desert legumes. Mature seeds were collected in summer 2017 and germinated within one week of collection (fresh) and after six months (dry-storage) under two temperature and two light regimes. Seed weight of two species increased 22-55% within 24 hours of water imbibition but others increased ≤ 7%. Germination ranged from 0-32% in fresh and 2-92% in dry-stored seeds, indicating a mix of non- and physically-dormant seeds at maturity. Dry-storage at ambient room temperature was effective at relieving dormancy, though the extent was species-dependent. Germination percentage increased in response to light exposure during incubation, while the effect of temperature was species-dependent. This variable response to dormancy alleviation may assist to spread the population risk of seedling survival in the harsh and variable environment of the Arabian desert.

The kinetics of ageing in dry-stored seeds: a comparison of viability loss and RNA degradation in unique legacy seed collections.

Determining seed longevity by identifying chemical changes that precede, and may be linked to, seed mortality, is an important but difficult task. The standard assessment, germination proportion, reveals seed longevity by showing that germination proportion declines, but cannot be used to predict when germination will be significantly compromised. Assessment of molecular integrity, such as RNA integrity, may be more informative about changes in seed health that precede viability loss, and has been shown to be useful in soybean. A collection of seeds stored at 5 °C and 35-50 % relative humidity for 1-30 years was used to test how germination proportion and RNA integrity are affected by storage time. Similarly, a collection of seeds stored at temperatures from -12 to +32 °C for 59 years was used to manipulate ageing rate. RNA integrity was calculated using total RNA extracted from one to five seeds per sample, analysed on an Agilent Bioanalyzer. Decreased RNA integrity was usually observed before viability loss. Correlation of RNA integrity with storage time or storage temperature was negative and significant for most species tested. Exceptions were watermelon, for which germination proportion and storage time were poorly correlated, and tomato, which showed electropherogram anomalies that affected RNA integrity number calculation. Temperature dependencies of ageing reactions were not significantly different across species or mode of detection. The overall correlation between germination proportion and RNA integrity, across all experiments, was positive and significant. Changes in RNA integrity when ageing is asymptomatic can be used to predict onset of viability decline. RNA integrity appears to be a metric of seed ageing that is broadly applicable across species. Time and molecular mobility of the substrate affect both the progress of seed ageing and loss of RNA integrity.

Exploring the fate of mRNA in aging seeds: protection, destruction, or slow decay?

Seeds exist in the vulnerable state of being unable to repair the chemical degradation all organisms suffer, which slowly ages seeds and eventually results in death. Proposed seed aging mechanisms involve all classes of biological molecules, and degradation of total RNA has been detected contemporaneously with viability loss in dry-stored seeds. To identify changes specific to mRNA, we examined the soybean (Glycine max) seed transcriptome, using new, whole-molecule sequencing technology. We detected strong evidence of transcript fragmentation in 23-year-old, compared with 2-year-old, seeds. Transcripts were broken non-specifically, and greater fragmentation occurred in longer transcripts, consistent with the proposed mechanism of molecular fission by free radical attack at random bases. Seeds died despite high integrity of short transcripts, indicating that functions encoded by short transcripts are not sufficient to maintain viability. This study provides an approach to probe the asymptomatic phase of seed aging, namely by quantifying transcript degradation as a function of storage time.

Effect of population, collection year, after-ripening and incubation condition on seed germination of Stipa bungeana

Knowledge of the germination behavior of different populations of a species can be useful in the selection of appropriate seed sources for restoration. The aim of this study was to test the effect of seed population, collection year, after-ripening and incubation conditions on seed dormancy and germination of Stipa bungeana, a perennial grass used for revegetation of degraded grasslands on the Loess Plateau, China. Fresh S. bungeana seeds were collected from eight locally-adapted populations in 2015 and 2016. Dormancy and germination characteristics of fresh and 6-month-old dry-stored seeds were determined by incubating them over a range of alternating temperature regimes in light. Effect of water stress on germination was tested for fresh and 6-month-old dry-stored seeds. Seed dormancy and germination of S. bungeana differed with population and collection year. Six months of dry storage broke seed dormancy, broadened the temperature range for germination and increased among-population differences in germination percentage. The rank order of germination was not consistent in all germination tests, and it varied among populations. Thus, studies on comparing seed dormancy and germination among populations must consider year of collection, seed dormancy states and germination test conditions when selecting seeds for grassland restoration and management.

Effects of pectinase, BAP and dry storage on dormancy breaking and emergence rate of Crataegus pseudoheterophylla Pojark.

Germination rates of Crataegus pseudoheterophylla are low and may be restricted by the presence of a hard endocarp and embryo dormancy. We examined the effects of pectinase [0, 0.5, 1, or 2 % (w/v)], benzylaminopurine (BAP) (0, 100, 200, 400, or 500 mg l−1) and dry storage (6, 9, or 12 months), on water uptake percentage (WUP) and seedling emergence rates with the endocarp intact or removed. Following treatments, seeds were subjected to a cold–warm–cold–warm–cold alternating temperature stratification regime, and then germinated at 23 °C for up to 90 days. The highest germination percentage (GP) of 37.7 and 32.7 % were obtained in seeds without endocarp treated at 500 mg l−1 BAP and dry-stored seeds for 12 months, respectively. WUP imbibed (96 h) in seeds with and without endocarp was 26.7 and 39.4 %, respectively, and the highest WUP was achieved in a period of 12 months (81 %). These results revealed that the application of BAP, pectinase, and dry storage significantly increased GP in C. pseudoheterophylla, probably mainly through dormancy-mediated processes. The results of the study confirmed that the seeds were semi-permeable by water.

Ex-situ Seed Conservation of Endangered Key Tree Cactus (Pilosocereus robinii)

Ex-situ seed collections are fundamental to the conservation of threatened and endangered plant species. We tested whether or not seeds of the U.S. endangered tree cactus, Pilosocereus robinii, withstand orthodox storage conditions of low humidity (25%RH) and freezing temperatures (-20°C). Mean final germination of fresh seeds and seeds stored under low humidity and low temperature for 1 and 28 weeks ranged from 92 to 96%. Mean final germination did not differ significantly across storage conditions. Seed germination rate exhibited small, but significant differences across storage conditions. Seeds stored under dry conditions of low humidity and ambient temperature germinated significantly faster than dry-stored seeds maintained at freezing temperatures and fresh seeds. Because orthodox methods of drying and freezing can be used to store seeds of Pilosocereus robinii, ex-situ seed banking can effectively assist the conservation and regeneration of this endangered species.

Effects of sand burial, soil water content and distribution pattern of seeds in sand on seed germination and seedling survival of Eremosparton songoricum (Fabaceae), a rare species inhabiting the moving sand dunes of the Gurbantunggut Desert of China

Sand burial, persistent seed bank and soil water content (SWC) are three factors that potentially can affect regeneration in sand dune plant populations. To evaluate the effects of these three factors on population regeneration of Eremosparton songoricum, a rare and endangered legume, we investigated seed germination, seedling emergence and seedling survival in greenhouse and controlled field experiments in different sand dunes microsites. Freshly matured seeds are physically dormant, and the highest germination was only 9.3 ± 5.8% at 25/10°C. Seed germination occurred at burial depths from 0 to 10 cm, but the maximum depth from which seedlings emerged was 6 cm; from 1 to 6 cm, the deeper the burial, the lower the percentage of seedling emergence. Only 36.2% of the total soil seed banks occurred at depths of 0–6 cm. For artificially sown seeds at different dune microsites, mean seedling emergence percentage was 6.8%. Of 150 seedlings that emerged in the field investigation at the study site, only those germinating in flat sandy areas survived, and mean survival percentage was only 2.0%. Thus, the proportion of non-dormant seeds in soil seed banks that developed into seedlings and survived to the end of the growing season was only 0.2%. Minimum SWC for seed germination, seedling emergence and seedling survival was 2.0%. During monitoring of emergent seedlings in the field, low seedling recruitment was at least partly due to the rate of root extension (1.6 ± 0.3 cm day−1) into the sandy soil, which was slower than that of the downward movement of plant-available moisture (2.8 ± 0.6 cm day−1). Thus, population regeneration under natural conditions rarely occurred via sexual reproduction, owing to the limited water resources available for seedling establishment. Rational field seeding practices, including manually scarified or dry stored seeds before sowing, sowing the seeds at right time and suitable place, are suggested for ecological restoration of endangered E. songoricum populations.

Germination of 151-year old Acacia spp. seeds

A collection of seeds from five Acacia species was made in Egypt in 1856. Since then, the seeds have been stored at room temperature in different Swedish museums. Due to the extreme longevity within the seeds of Acacia and related species, germination tests were performed on the now 151-year old seed. Seeds of two of the five species tested germinated. The first, Acacia farnesiana (L.) Willd., had two seeds germinate, and Acacia melanoxylon R. Br. ex Ait. f. had one seed germinate. In addition, DNA was extracted from the aged seed and DNA preservation was analyzed. Four of the tested species displayed well preserved DNA, whereas DNA from Albizia lebbeck (L.) Benth. showed signs of degradation. The 151-year longevity of the Acacia seeds is among the longest of dry-stored seeds reported. Several independent studies now report on extreme survival capacity for Acacia and related genera suggesting that these genera are suitable for studies on the characteristics of seeds with long storage performance. The results also demonstrate that herbaria and seed collections stored in museums and institutional depositories can be alternate sources of plants genetic material and should be given conservation attention.

Germination of Ocotea pulchella (Nees) Mez (Lauraceae) seeds in laboratory and natural restinga environment conditions

The germination response of Ocotea pulchella (Nees) Mez seeds to light, temperature, water level and pulp presence is introduced. The laboratory assays were carried out in germination chambers and thermal-gradient apparatus, whereas the field assays were performed in environments with distinct light, temperature and soil moisture conditions within a permanent parcel of Restinga forest of the Parque Estadual da Ilha do Cardoso, Cananéia, São Paulo. The seeds do not exhibit dormancy, they are non photoblastic, and a loss of viability in dry stored seeds can be related to a decrease in water content of the seed. The presence of the pulp and the flooded substratum influenced negatively the germination of O. pulchella seeds tested in the laboratory. Otherwise, light and temperature probably are not limiting factors of the germination of O. pulchella seeds in the natural environment of Restinga. The optimum temperature range for germination of Ocotea pulchella seeds was 20 to 32 degrees C, the minimum or base temperature estimated was 11 degrees C and the maximum ranged between 33 and 42 degrees C. The isotherms exhibited a sigmoidal pattern well described by the Weibull model in the sub-optimal temperature range. The germinability of O. pulchella seeds in the understorey, both in wet and dry soil, was higher than in gaps. Germination was not affected by fluctuations in soil moisture content in the understorey environment, whereas in gaps, germination was higher in wet soils. Thus, the germination of this species involves the interaction of two or more factors and it cannot be explained by a single factor.

Seed germinability in Musa velutina Wendl. & Drude is markedly lowered by 1 week in dry-storage

SUMMARYWe investigated the effects of dry-storage of Musa velutina seeds on seed and embryo germination. Seeds were collected immediately after harvest and stored in dry vermiculite at 25°C, in the dark, for 0, 1, 2, or 4 months. The germinability of dry-stored seeds was assessed by incubation in vermiculite at 25°C for 4 months, with 75% [(w/w); –0.01 MPa] moisture content to promote embryo development in viable seeds. Seeds that had not been dry-stored and stored in vermiculite at 75% (w/w) moisture content for 4 months showed 90% germination by 20 d after sowing, but no seeds that had been dry-stored for longer than 1 month germinated. Seeds were also dry-stored at 25°C, in the dark, in Petri dishes for 0, 1, 2, 3, or 4 weeks after harvest and the embryos removed from these seeds were cultured on MS medium. All embryos that had been isolated from seeds at harvest (i.e., 0 weeks in dry-storage) germinated during embryo culture. However, embryos removed from seeds that had been dry-stored for 1 week showed a substantial decrease in both size and germinability. Seeds were also stored at different moisture contents for 4 months after harvest. No seeds that had been stored at 0% moisture content (i.e., dry) germinated, but > 85% of seeds stored at ≥ 25% (w/w) moisture contents germinated. Higher moisture contents increased the uniformity of seed germination, showing that M. velutina seeds rapidly lose their germinability through dehydration, indicating that they are sensitive to desiccation.

Environmental signals for seed germination reflect habitat adaptations in four temperate Caryophyllaceae

Summary 1Requirements for dormancy break and seed germination are specific for all species and depend chiefly on phylogeny, geographical distribution, habitat preference and life cycle. Studying germination requirements of closely related species with a similar geographic distribution allows one to attribute variation in germination requirements to differences in habitat preference between the species. 2We investigated requirements for dormancy break and the effect of environmental signals on induction of germination in seeds of four closely related Caryophyllaceae species growing in a variety of habitats (Moehringia trinervia, Stellaria holostea, S. nemorum and S. graminea). The species studied depend on disturbances in the vegetation for seed germination and subsequent seedling establishment. 3Seedlings of all four species emerged both in summer and spring. Stellaria nemorum and M. trinervia, both growing in temperate forests, emerged mainly in summer under a closed forest canopy. Seeds of S. graminea, occurring in grasslands, did germinate in summer at an open site, but could not germinate under a closed forest canopy. Seedlings of S. holostea were observed in late summer when buried at an open site or in early spring when sown in a forest patch. 4Seeds of S. holostea and M. trinervia were completely dormant at dispersal in early summer, while germination was low in fresh seeds of S. graminea and S. nemorum. Dormancy was broken, to a certain extent, during all three after-ripening treatments applied (dry storage, cold and warm stratification). 5The effect of three gap-detection signals (light, fluctuating temperatures, nitrates) on germination of fresh and dry stored seeds was tested. Seeds of S. holostea only germinated in response to daily fluctuating temperatures. Although light was the most important signal affecting germination of S. graminea and M. trinervia, we also observed a positive effect of fluctuating temperatures and nitrates on germination. The effect of fluctuating temperatures on germination of S. nemorum was small in both light and dark incubated seeds. Seed germination in this species generally occurred in response to addition of light and nitrates. 6This study on dormancy breaking and germination requirements of the four species enabled us to expose, sometimes subtle, differences in germination requirements. These contrasting germination patterns were related to differences in the species’ habitat preferences.

Changes in late embryogenesis abundant proteins and a small heat shock protein during storage of beech ( Fagus sylvatica L.) seeds

Beech seed physiology, including the effect of stress proteins like late embryogenesis abundant (LEA) and small heat shock proteins (sHSP) on viability during storage, is not fully understood. Four lots of beech ( Fagus sylvatica L.) seeds have been stored for 1, 4, 6 and 8 years at −10 °C and 8–9% moisture content (MC). Under these conditions, the germination capacity ranges from 81.5% to 100% in the youngest seeds. However, the seeds decrease in vigour with prolonged time of storage. Dehydrins and dehydrin-like proteins were identified both in cotyledons and embryonic axes of the dry stored seeds. In general, decreased contents of LEA proteins as well as reduced content of total soluble protein were detected during prolonged storage. The contents of soluble proteins in embryonic axes and nearly all detected dehydrins and dehydrin-like proteins were correlated with germination capacity. Moreover a sHSP with molecular mass of approximately 22 kDa was identified. The largest content of this protein was observed in the oldest seeds, especially in embryonic axes. The proteins identified may play a protective role during water deficit and storage.

Psychotria hoffmansegiana (Willd ex Roem. & Schult.) Mull. Arg. and Palicourea marcagravii st. Hil. (Rubiaceae): potential for forming soil seed banks in a brazilian Cerrado

The germinability of artificially buried Psychotria hoffmansegiana and Palicourea marcagravii seeds in Cerrado soil was tested, with the aim of evaluating whether dispersed seeds may be able to form a soil seed bank. The assays were carried out at a Cerrado Reserve in São Paulo State, Brazil. Seed samples were placed in nylon bags and buried at two different depths and in two different sites. Samples were periodically exhumed and germination tests were performed with both exhumed and dry stored seeds. In general, soil storage favoured seed survival and germination when compared to dry stored seeds. The seed germination was little affected by soil depth and by burial environment. Seeds of both species remained viable for at least 13 months, considering the time lapse between the collection and the end of the germination tests. It was suggested that both species can potentially form a persistent soil seed bank in Cerrado.

Storage in cerrado soil and germination of Psychotria vellosiana (Rubiaceae) seeds

The regeneration of plant communities from seed depends, to a large extent, on the capacity of the seed remaining viable in the soil. The viability and germination of artificially buried Psychotria vellosiana seeds in cerrado soil were studied, with the purpose of discovering some physio-ecological aspects of dispersed seeds and evaluating their potential to constitute a soil seed bank. Seed samples were placed in nylon envelopes and buried in the soil of a Cerrado reserve at two different depths and sites. Buried seeds were retrieved periodically and tested for germination along with dry-stored seeds. In general, there was a reduction in seed germination with storage time, both in soil and dry stored conditions, and in some assays exhumed seeds germinated faster than dry stored ones. In general the soil storage favoured seed viability of ungerminated seeds as compared to dry stored ones, with the seeds remaining partially viable after 10 months of storage. The lack of germination of viable seeds suggests that seeds showed true dormancy and/or required an extended time to germinate. It was observed that some seeds had germinated while buried and such in situ germination tended to increase with rainfall. The water availability in the soil might be a limiting factor for successful germination of P. vellosiana in the field, and the seeds may constitute a persistent soil seed bank in the cerrado as dispersed seeds remain viable in the soil until the following period of seed dispersal.

Does lignum rely on a soil seed bank? Germination and reproductive phenology of Muehlenbeckia florulenta (Polygonaceae)

Tangled lignum (‘lignum’) is a dioecious, multi-stemmed woody shrub that is common in flood-prone areas of inland Australia, including the Murray–Darling Basin. It is often leafless during dry periods, but maintains vegetative growth by stem layering, and responds rapidly to rainfall or flooding by production of shoots, leaves and flowers. This study considers the viability of lignum seeds (contained in achenes) under various conditions of temperature, light, moisture and storage or burial. The seeds are not innately dormant, and germinate within 14 days under ideal conditions. From 66 to 86% of fresh and dry-stored seeds germinate in fluctuating temperatures (15°C/5°C, 24°C/10°C, 31°C/15°C), and optimally at 24°C/10°C, given moisture and light. They also germinate in water (56% success), and remain buoyant for 5–25 days. Germination is inhibited by constant temperatures of 12 and 24°C (4.0–4.8% success) and continuous darkness (6.0–56.0% success), but increases on return to light. Seed viability is depressed by 10% after 70-day dry storage and by 48% after 92-day burial in soil over winter. In one year’s (2002) observations of a population on the River Murray floodplain near Morgan, South Australia, winter- and spring-seeding plants produced viable seeds 14–30 days after anthesis, and although rainfall in winter (July) produced a pulse of seedlings, none became established. Achenes were shed soon after maturation, but soil samples revealed very few germinable seeds. It therefore appears that the seeds do not persist for long on the mother plant or in the soil. The persistence of lignum in environments prone to erratic droughts and floods appears to depend mainly on its capacity to tolerate drought, maintain vegetative growth and respond quickly to watering.

The role of temperature in the regulation of dormancy and germination of two related summer-annual mudflat species

Dormancy and germination requirements were investigated in seeds (achenes) of the closely-related annuals Bidens cernua and Bidens tripartita (Asteraceae). They showed clear differences in their temperature requirements for germination, their dormancy and seed longevity in soil. In B. cernua seeds, primary dormancy was relieved when stratified at 3, 8, and 12 °C, as seeds germinated to a maximum of more than 80% (3 °C and 8 °C) and 20% (12 °C), while temperatures of 15 °C and 18 °C had no effect. Secondary dormancy was induced after 20 weeks at 12 °C. Temperatures between 3 and 18 °C were effective in relieving dormancy in B. tripartita seeds as they germinated to more than 60% regardless of stratification temperature. With prolonged incubation time, dormancy was induced at 18 °C. Both species exhibited an annual dormancy cycle. B. cernua seeds came out of dormancy in spring at temperatures <15 °C and dormancy was induced in summer (>15 °C). In late summer, seeds were completely dormant before temperatures of <7 °C led to a relief of secondary dormancy. B. tripartita seeds came out of both primary and secondary dormancy when ambient temperatures were <12 °C in autumn. At temperatures >7 °C in spring and summer, dormancy was induced. Nevertheless, B. tripartita seeds could germinate (>40%) during the whole year at high and fluctuating temperatures. B. tripartita had the potential to accumulate a persistent seed bank, while buried B. cernua seeds were all dead after 20 months. Germination tests with dry-stored seeds showed that a fluctuating-temperature amplitude of ≥8 °C (mean 22 °C) led to a significantly higher germination (40%) of B. tripartita seeds, while B. cernua seeds did not germinate even at high amplitudes. Stratified B. tripartita seeds germinated at high constant temperatures >21 °C, while B. cernua seeds showed a nearly absolute requirement for fluctuating temperatures.

Environmental factors affecting germination of apple of Peru

Abstract Laboratory and field experiments were conducted to determine the effects of several environmental factors on seed germination and seedling emergence of the invasive weed, apple of Peru. The anatomy of the seed was also investigated in this study. The anatomy of the seed is similar to that of an eggplant (Solanum melongena L.) seed. The seed is albuminous, and consists of a seed coat, endosperm, and an embryo. The seed coat, which consists of both outer and inner integuments, is relatively thick. Fresh and dry stored seeds exhibited strong dormancy. Hot water treatment did not affect the seed germination in the light, but significantly (P < 0.05) reduced the germination rate in the dark. Dry-heat treatment had no significant effect on seed germination in the dark, but it significantly (P < 0.05) increased the germination rate in the light. Cold stratification alone did not influence seed germination under constant temperature (25 C) but affected it under alternating temperature (25–15 C). However,...

Ecological genetics of seed germination regulation in Bromus tectorum L. : II. Reaction norms in response to a water stress gradient imposed during seed maturation.

The probability that a seed will germinate depends on factors associated with genotype, maturation environment, post-maturation history, and germination environment. In this study, we examined the interaction among these sets of factors for 18 inbred lines from six populations of Bromus tectorum L., a winter annual grass that is an important weed in the semi-arid western United States. Seeds of this species are at least conditionally dormant at dispersal and become germinable through dry-afterripening under summer conditions. Populations and inbred lines of B. tectorum possess contrasting dormancy patterns. Seeds of each inbred line were produced in a greenhouse under one of three levels of maturation water stress, then subjected to immediate incubation under five incubation regimes or to dry storage at 20°C for 4 weeks, 12 weeks, or 1 year. Dry-stored seeds were subsequently placed in incubation at 20/30°C. Narrow-sense heritability estimates based on parent-offspring regressions for germination percentage of recently harvested seeds at each incubation temperature were high (0.518-0.993). Germination percentage increased with increasing water stress overall, but there were strong interactions with inbred line and incubation temperature. Inbred lines whose seeds were non-dormant over the full range of incubation temperatures when produced at low maturation water stress showed reaction norms characterized by little or no change as a function of increasing stress. For inbred lines whose dormancy status varied with incubation temperature, incubation treatments where seeds exhibited either very low or very high levels of dormancy showed the least change in response to maturation water stress. Inbred lines also varied in their pattern of dormancy loss during storage at 20°C, but maturation water stress had only a minor effect on this pattern. For fully afterripened seeds (1 year in storage at 20°C), inbred line and maturation water stress effects were no longer evident, indicating that differences in genotype and maturation environment function mainly to regulate dormancy and dormancy loss in B. tectorum, rather than to mediate response patterns of non-dormant seeds.