Ecophysiology of embryo development and seed germination of the European woodland herbaceous perennial Corydalis cava (L.) Schweigg. & Körte subsp. cava (Fumariaceae)

In this study we examined the germination ecology with special reference to the temperature requirements for embryo development and germination of Corydalis cava subsp. cava, under both outdoor and laboratory conditions. Corydalis cava is a spring flowering woodland tuberous geophyte widely distributed across Europe. Germination phenology, including embryo development and radicle and cotyledon emergence, was investigated in a population growing in northern Italy. Immediately after harvest, seeds of C. cava were sown both in the laboratory under simulated seasonal temperatures and naturally. Embryos, undifferentiated at the time of seed dispersal, grew during summer and autumn conditions, culminating in radicle emergence in winter, when temperatures fell to ca 5°C. Cotyledon emergence also occurred at ca 5°C, but first emergence was delayed until late winter and early spring. Laboratory experiments showed that high (summer) followed by medium (autumn) and low temperatures (winter) are needed for physiological dormancy loss, embryo development and germination respectively. Unlike seeds of C. cava that germinated in winter, in other Corydalis species radicle emergence occurred in autumn (C. flavula) or did not depend on a period of high summer temperature to break dormancy (C. solida). Our results suggest that subtle differences in dormancy and germination behavior between Corydalis species could be related to differences in their geographical distribution.     

Triacylglycerol phase and ‘intermediate’ seed storage physiology: a study of Cuphea carthagenensis

Seeds with ‘intermediate’ storage physiology store poorly under cold and dry conditions. We tested whether the poor shelf life can be attributed to triacylglycerol phase changes using Cuphea carthagenensis (Jacq.) seeds. Viability remained high when seeds were stored at 25°C, but was lost quickly when seeds were stored at 5°C. Deterioration was fastest in seeds with high (≥0.10 g g⁻¹) and low (0.01 g g⁻¹) water contents (g H₂O g dry mass⁻¹), and slowest in seeds containing 0.04 g g⁻¹. A 45°C treatment before imbibition restored germination of dry seeds by melting crystallized triacylglycerols. Here, we show that the rate of deterioration in C. carthagenensis seeds stored at 5°C correlated with the rate that triacylglycerols crystallized within the seeds. Lipid crystallization, measured using differential scanning calorimetry, occurred at 6°C for this species and was fastest for seeds stored at 5°C that had high and very low water contents, and slowest for seeds containing 0.04 g g⁻¹. Germination decreased to 50% (P50) when between 16 and 38% of the triacylglycerols crystallized; complete crystallization took from 10 to over 200 days depending on water content. Our results demonstrate interactions between water and triacylglycerols in seeds: (1) water content affects the propensity of triacylglycerols to crystallize and (2) hydration of seed containing crystallized triacylglycerols is lethal. We suggest that these interactions form the basis of the syndrome of damage experienced when seeds with intermediate storage physiologies are placed in long-term storage.     

Effect of Temperature Regimes on Germination of Dimorphic Seeds of Atriplex prostrata

Dimorphic seeds of Atriplex prostrata were removed from cold dry storage monthly over a one year period to test for fluctuations in seed dormancy and germination rate. For each seed type, four replicates of 25 seeds were exposed to four alternating night/day temperature regimes mimicking seasonal fluctuations in Ohio: 5/15 °C; 5/25 °C; 15/25 °C and 20/35 °C with a corresponding 12-h photoperiod (20 μmol m⁻² s⁻¹; 400 – 700 nm). We found a significant three-way interaction of seed size, temperature and month for both percent germination and the rate of germination. Large seeds showed the greatest germination at the 20/35 °C and 5/25 °C temperature regimes and small seeds at the 5/25 °C regime. Large seeds had greater germination at all temperatures as compared to small seeds. Large seeds had the fastest germination rates at 20/35 °C followed by 5/25 °C whereas small seeds had the fastest rates at 5/25 °C followed by 20/35 °C. This revised version was published online in July 2006 with corrections to the Cover Date.     

Variation in dormancy and germination in three co-occurring perennial forest herbs

Mesic deciduous forest herbs often disperse seed with morphophysiological dormancy (MPD) that prevents germination during unfavorable periods for seedling survival. However, for seeds of some species with MPD, seasonal separation of root and shoot emergence and variation in dormancy levels can complicate interpretation of seedling emergence timing in the field. We tested whether dormancy-break and germination requirements differed among co-occurring perennial forest herbs, Actaea racemosa, Hydrastis canadensis, and Sanguinaria canadensis, which are wild-harvested for their medicinal properties and known to have MPD. Seeds of all species exhibited a summer → autumn → winter requirement for seedling emergence in spring. However, species differed in seed-bank persistence due to variation in primary dormancy levels and stratification requirement of seeds. A. racemosa and H. canadensis can form short-term persistent seed bank, whereas S. canadensis can form a long-term persistent seed-bank, regardless of whether elaiosomes were removed from seeds prior to burial. A. racemosa seeds are dispersed in autumn with weak physiological dormancy, as seeds germinated to high rates at 15/6°C after 8 weeks. In contrast, most seeds of the summer dispersed species, H. canadensis and S. canadensis, require summer temperatures to overcome physiological dormancy. Consequently, seedling emergence is reduced and delayed by 1 year if seeds are not sown immediately following the period of natural dispersal. Seedling emergence was much lower in the field than in controlled conditions for all species, especially in the small-seeded A. racemosa. Interspecific variation in dormancy levels and germination traits must be considered when establishing populations for conservation purposes and in understanding recruitment limitation in perennial forest herbs.     

Combinational dormancy in seeds of Sicyos angulatus (Cucurbitaceae,tribe Sicyeae)

Seeds with a water‐impermeable seed coat and a physiologically dormant embryo are classified as having combinational dormancy. Seeds of Sicyos angulatus (burcucumber) have been clearly shown to have a water‐impermeable seed coat (physical dormancy [PY]). The primary aim of the present study was to confirm (or not) that physiological dormancy (PD) is also present in seeds of S. angulatus. The highest germination of scarified fresh (38%) and 3‐month dry‐stored (36%) seeds occurred at 35/20°C. The rate (speed) of germination was faster in scarified dry‐stored seeds than in scarified fresh seeds. Removal of the seed coat, but leaving the membrane surrounding the embryo intact, increased germination of both fresh and dry‐stored seeds to > 85% at 35/20°C. Germination (80–100%) of excised embryos (both seed coat and membrane removed) occurred at 15/6, 25/15 and 35/20°C and reached 95–100% after 4 days of incubation at 25/15 and 35/20°C. Dry storage (after‐ripening) caused an increase in the germination percentage of scarified and of decoated seeds at 25/15°C and in both germination percentage and rate of excised embryos at 15/6°C. Eight weeks of cold stratification resulted in a significant increase in the germination of scarified seeds at 25/15 and 35/20°C and of decoated seeds at 15/6 and 25/15°C. Based on the results of our study and on information reported in the literature, we conclude that seeds of S. angulatus not only have PY, but also non‐deep PD, that is, combinational dormancy (PY + PD).     

Seed dormancy and germination in the giant Himalayan lily (Cardiocrinum giganteum var. giganteum): an assessment of its potential for naturalization in northern Japan

Understanding the potential for ornamental plant species to become naturalized in a nonnative habitat requires information on seed germination in order to help predict responses of the species to the natural environmental conditions of its new habitat. Cardiocrinum giganteum var. giganteum, which is native to the Himalayas, has been introduced as an ornamental plant in temperate regions of the world, and was categorized recently as invasive in New Zealand. Seed germination requirements of the species were determined under natural conditions in Hokkaido, Japan, to assess its potential to become naturalized in this region of Japan. Mature seeds were collected from its native range in the Indian Himalayas. At maturity in autumn, seeds had underdeveloped embryos, which grew in the second autumn and winter after exposure to summer temperatures. Radicles and cotyledons emerged in late winter and spring. Thus, an 18?C19?month period was required from dispersal to seed germination. Under laboratory conditions, this period could be shortened to 10?C11?months in a 25/15?°C (120?days)????15/5?°C (90?days)????0?°C (90?days)????15/5?°C (60?days) temperature sequence. GA₃ did not substitute for the above temperature requirements. These temperature requirements for seed germination of C. giganteum var. giganteum are very similar to those of its native Japanese congener C. cordatum var. glehnii. Seeds of both taxa have deep simple morphophysiological dormancy. The close similarity in the requirements for regeneration from seeds of the two taxa suggests that the seed stage of the life cycle is not an impediment to the naturalization of the giant Himalayan lily in northern Japan.     

From seed to seedling: A critical transitional stage for the Mediterranean psammophilous species Dianthus morisianus (Caryophyllaceae)

Abstract

Seed germination, seedling emergence and seed persistence in the soil were investigated for Dianthus morisianus (Caryophyllaceae), a psammophilous endemic species of Sardinia. Stored and freshly collected seeds were incubated in a range of constant temperatures (5–25°C) and an alternating temperature regime (25/10°C). The effect of seed burial depth on seedling emergence was investigated under controlled environmental conditions. Seed persistence in the soil was verified by in situ experimental seed burials. Seeds of this species were non-dormant, and all seed lots germinated both in the light and darkness, mainly at low temperatures (≤20°C), with a maximum at 15°C (≥95%). Optimal seedling emergence was obtained when seeds were buried at a depth of 1–2 cm, and a declining emergence with increasing depth was observed. D. morisianus was also unable to form a persistent soil seed bank. The fate of the seeds that, after dispersal, do not emerge from the soil in the spring is, therefore, presumably to die before the next favourable growing season.     

Germination responses to temperature responsible for the seedling emergence seasonality ofPrimula sieboldii E. Morren in its natural habitat

Temperature requirements for the breaking of seed dormancy and germination inPrimula sieboldii E. Morren and the annual surface-soil temperature regime in one of its natural habitats were investigated in order to clarify the germination responses determining the seedling emergence seasonality of the species. In a grassland nature reserve in an abandoned flood plain of the Arakawa River, natural seedling emergence of the species was shown to be restricted to mid- to late-spring before the closure of seasonal vegetational gaps, when the daily mean soil surface temperature reached about 15°C, accompanied by large daily fluctuations of about 10°C. Mature seeds collected in late June were never able to germinate at any constant temperature in the range of 8–40°C unless they had been previously subjected to moist-chilling treatment. The proportion of seeds which were released from dormancy increased with increasing duration of the moist-chilling treatment at 2°C, 70–85% of seeds becoming germinable at 16–28°C after 12 weeks of pretreatment at 2°C. The thermal time required for the germination of the thus-pretreated seed population was 905–1690 Kh with a base temperature of around 5°C. Fluctuating temperatures between 24°C and 16 or 12°C had a remarkable dormancy-breaking effect, inducing considerably quick germination in most of the seeds previously subjected to 2°C moist-chilling for 8 weeks.     

GERMINATION ECOPHYSIOLOGY OF HYDROPHYLLUM APPENDICULATUM,A MESIC FOREST BIENNIAL

In north central Kentucky, seeds of the mesic forest biennial Hydrophyllum appendiculatum Michx., are innately dormant at maturity in June. Under natural and simulated seasonal temperature changes, dormancy break occurred in two stages. Root dormancy was broken by high summer temperatures, and shoot dormancy was broken by low winter temperatures. Consequently, roots emerged from seeds during autumn, and cotyledons emerged the following spring. A 90-day warm (30/15 C) stratification treatment broke root dormancy, but the roots emerged only after transfer to lower temperatures. After the warm stratification treatment, roots emerged from 93, 73, 6 and 9% of the seeds incubated at 5, 15/6, 20/10 and 30/15 C (12/12 hr), respectively. Zero, 28, 56 and 84 days of cold (5 C) stratification of seeds with emerged roots resulted in 9, 21, 49 and 82% cotyledon emergence, respectively, at 20/10 C. Thus, H. appendiculatum exhibits a type of morpho-physiological dormancy known as epicotyl dormancy. Although many seeds germinate the first year, others remain dormant and germinate in successive years until the fourth season after ripening.     

Seed germination time course and seedling development of Clintonia udensis Trautv. et Mey. (Uvulariaceae): a typical cool temperate woodland perennial in Japan

Seed germination time course and seedling development mechanisms of Clintonia udensis Trautv. et Mey. (Uvulariaceae) were investigated under experimental condition. Seed germination tests were carried out under four thermal regimes, i. e. 10, 15, 20, and 25°C, after seeds were harvested, and stored at 5°C in wet conditions for 6 months under light‐exposed or shaded conditions. Approximately 63% of all seeds produced had the potential to germinate beyond 4 years and 6 months. The developmental process after germination continued for over 2 years. Phase I: the radicle first breaks through the seed coat 2 years after fructification. Phase II: the radicle becomes much larger with a hypocotyle. Phase III: part of the cotyledon elongates over 20 mm. Phase IV: the plumule further develops in two steps, i. e. the plumule is first formed, while cotyledon is disappearing, and then the plumule appears with second and third radicles, growing with cotyledon.     

Improving germination and vigour of aged and stored onion seeds by matriconditioning

Germination and vigour of accelerated aged (AA) and naturally stored onion seeds were examined. Accelerated ageing was conducted at 40 °C and 100 % relative humidity (RH). Non aged seeds were stored for 34 months at 3 or 15 °C and 40, 60 or 90 % RH. To restore seed viability, stored and aged seeds were matriconditioned with Micro-Cel E. A distinct loss of germination was observed after 5 days of accelerated ageing. Naturally stored seeds maintained high viability for 34 months, when stored at 3 °C and 40, 60 and 90 % RH or at 15 °C and 40 %. An increase of RH to 60 and 90 % at 15 °C caused loss of germination and vigour. Matriconditioning improved germination and increased endogenic ethylene release and in vivo ACC oxidase activity of both aged and stored seeds.     

The effect of sowing pre-germinated seeds of lettuce (Lactuca sativa) on seedling emergence

Glasshouse and field experiments were conducted to investigate the effects of sowing both untreated and pre-germinated seeds, with or without a gel carrier, and also pelleted seeds into soils of different moisture contents and at different temperatures on seedling emergence of lettuce cvs Cobham Green and Avondefiance. Pre-germinated seeds with radicles 1–2 mm long gave, on average, 15 and 4% higher final percentage emergence than untreated and pelleted seeds respectively. Sowing pre-germinated seeds having radicles longer than 2 mm gave more variable levels of emergence and often reduced emergence, particularly when they were sown into dry or drying seedbeds. Increasing the rate of gel carrier from 0 to 30 ml m^_1 of row reduced emergence progressively from 67 to 30%. Pre-germinated seeds emerged 2–5 and 3-0 days earlier than untreated and pelleted seeds, respectively, at a soil temperature of 10 ^oC; at 15 ^oC the corresponding figures were 0–5 and 3–5 days. Sowing pre-germinated seeds reduced the spread (i.e. variability) of emergence by an average of 37 and 47% compared with untreated and pelleted seeds, respectively.     

Rodent seed predation and seedling recruitment in mesic grassland

Seedling recruitment of two grasses (Arrhenatherum elatius and Festuca rubra) and two herbs (Centaurea nigra and Rumex acetosa) was measured in areas with and without rodents to which seeds of each species were sown at three seed densities (1000, 10,000 and 50,000 seeds m⁻²) in two seasons (spring and autumn 1995). Seed removal was measured for 10-day periods and the fate of seedlings was followed for 15 months after sowing. The proportion of seed removed ranged from 6 to 85% and increased with increasing seed density for each species. Rodents had no effect on seedling emergence or survival in the spring sowing. In the autumn sowing, rodents reduced seedling emergence of all four species sown at 1000 and 10,000 seeds m⁻² but had no impact at 50,000 seeds m⁻², presumably because of microsite limitation. We suggest the difference between spring and autumn arose because emergence was seed limited in autumn but microsite limited in spring; microsite availability was higher in autumn because a summer drought killed plants, reduced plant biomass and opened up the sward. Fifteen months after the autumn sowing, fewer A. elatius and C. nigra seedlings survived on plots exposed to rodents. This result reflected not only the reduced seedling emergence but also increased seedling mortality (seedling herbivory) in sites exposed to rodents. In contrast, F. rubra and R.acteosa showed density-dependent seedling survival which compensated for initial differences in seedling emergence, so that no effect of rodents remained after 15 months. The results suggest that rodent seed predation and seedling herbivory exert strong effects on seedling recruitment of A.elatius and C. nigra when recruitment conditions are favourable (conditions that lead to high microsite availability) and may contribute to both species being maintained at low densities in the grassland. The results also demonstrate that highly significant impacts of rodent seed predation at the seedling emergence stage can disappear by the time of plant maturation. Received: 2 March 1998 / Accepted: 28 September 1998     

Comportamento Alla Germinazione Delle Cariossidi Delle Linee Primaverile e Invernale del Triticum Esaploide «Denti de Cani»

Abstract

The germination of spring and winter wheat lines of exaploid Triticum « Denti de Cani ». — The dormancy in the seeds of two lines of Triticum « Denti de Cani » (which is spontaneous in Sardinia), one with solid stem (CP line), a spring line, the other with hollow stem (CV line), an winter line, has been studied. Germination was carried out in the dark, in Petri dishes at the constant temperatures of 5°, 10°, 20°, 23°, 26°, 30° and 35°C, using full ripe seeds, and seeds in different stages of after-ripening up to one year of age. The increase in % germination, for increasing temperatures above 5°C, is clearly conditioned by the progress of after-ripening in the seeds. In fact it was seen that, in general for the two lines, percentages over 50% of seeds germinated at 3 days were reached: at 10° and 20° after 15 days from the full ripening; at 23°C after 30 days; at 26°C after 50 days; at 30°C after about 100 days and at 35°C only after about 4–5 months from the harvest. During the experiment at 5°C it was observed that, during the first year of life of seeds and especially in the CP line, this temperature produces a clear slowing down in germinations after first year from the ripening, only the CV seeds — not the CP which remain very much inhibited — reach germination values over 50% at 3 days. It has also been demonstrated that the CV are more sensitive than the CP, in the first initial period of after-ripening (15 and 30 days), to the non-inhibiting activity of low temperatures (5° and 10°C) and that, between these, the 10°C temperature promotes the germination more clearly than the 5°C temperature. The results obtained have shown that the dormancy wears off in the spring CP-line much more slowly than in the winter CV-line. The CP-seeds remain in a relative dormancy condition for a long time, which causes a significative delay in germination, up to 100 days from the full ripening stage.     

Morphophysiological dormancy in seeds of the ANA grade angiosperm Schisandra arisanensis (Schisandraceae)

We determined the kind of seed dormancy in Schisandra arisanensis, an ANA grade ([A]mborellales [N]ymphaeales [A]ustrobaileyales) angiosperm with medicinal value. Seeds have small underdeveloped embryos, and following seed maturity their length increased approximately 360% before radicle emergence. Germination was delayed 6–8 weeks, and the percentage and rate were much higher at 15/6, 20/10 and 25/15°C than at 30/20°C. For seeds incubated at 5/5°C (8 weeks) → 15/6°C (4 weeks) → 20/10°C (8 weeks) → 25/15°C (12 weeks) → 20/10°C (5 weeks), embryos grew at 15/6°C → 20/10°C, and almost all seeds that germinated (89%) did so at 20/10°C → 25/15°C. When seeds were incubated in a complementary temperature sequence, 25/15°C (12 weeks) → 20/10°C (8 weeks) → 15/6°C (4 weeks) → 5/5°C (9 weeks) → 15/6°C (4 weeks), embryos grew at 25/15°C → 20/10°C. Nearly all seeds that germinated (93%) did so at 25/15°C → 20/10°C and at 15/6°C following 9 weeks at 5/5°C. Based on the temperature requirements for embryo growth and seed germination, seeds of this species have non‐deep simple morphophysiological dormancy (C_1bB).     

Germination ecology of Central Asian Stipa spp: differences among species, seed provenances, and the importance of field studies

Stipa-species are wide-spread in Central Asia, but sexual reproduction in the dry steppes is rare. To facilitate conservation and restoration of these important rangelands, we studied germination characteristics of three common Mongolian Stipa-species under field- and lab conditions. Seeds of Stipa krylovii, Stipa gobica and Stipa glareosa were sown at the study site in Southern Mongolia over two consecutive years during which period tests were carried out to ascertain whether competition or herbivory are the main constraints of seedling establishment. In addition, we tested germination and seed viability in the laboratory under two different temperature regimes (20/10°C and 8/4°C), as well as the effect of cold-stratification. The lab experiments also included S. krylovii seeds originating from three climatically different provenances. None of the three Stipa-species seedlings emerged during the first 2 years of the field study. However, after an unusually intense rain event in the third year, 3% of S. krylovii, 0.6% of S. glareosa and 0.1% of S. gobica seeds germinated in the study plots. The factors ‘sowing-year’ and ‘vegetation’ significantly affected seedling emergence, whereas grazing had no effect at all. Under laboratory conditions a high percentage of viable seeds of S. gobica and S. glareosa germinated at both incubation temperatures, and cold-stratification had no effect on germination or viability. Germination of S. krylovii seeds required warmer temperatures and cold-stratification had a positive effect. Such evidence for dormancy was more pronounced in seeds from the moister, northern provenances. Germination of Stipa-species in the field is rare and only possible under exceptionally moist conditions. Conservation should thus concentrate on steppe conservation rather than on restoration. Where artificial reseeding is necessary, differences among species and also among different seed provenances should be taken into account.     

Ecological longevity of Polaskia chende (Cactaceae) seeds in the soil seed bank,seedling emergence and survival

• Soil seed banks are essential elements of plant population dynamics, enabling species to maintain genetic variability, withstand periods of adversity and persist over time, including for cactus species. However knowledge of the soil seed bank in cacti is scanty. In this study, over a 5‐year period we studied the seed bank dynamics, seedling emergence and nurse plant facilitation of Polaskia chende, an endemic columnar cactus of central Mexico.
• P. chende seeds were collected for a wild population in Puebla, Mexico. Freshly collected seeds were sown at 25 °C and 12‐h photoperiod under white light, far‐red light and darkness. The collected seeds were divided in two lots, the first was stored in the laboratory and the second was use to bury seeds in open areas and beneath a shrub canopy. Seeds were exhumed periodically over 5 years. At the same time seeds were sown in open areas and beneath shrub canopies; seedling emergence and survival were recorded over different periods of time for 5 years.
• The species forms long‐term persistent soil seed banks. The timing of seedling emergence via germination in the field was regulated by interaction between light, temperature and soil moisture. Seeds entered secondary dormancy at specific times according to the expression of environmental factors, demonstrating irregular dormancy cycling.
• Seedling survival of P. chende was improved under Acacia constricta nurse plants. Finally, plant facilitation affected the soil seed bank dynamics as it promoted the formation of a soil seed bank, but not its persistence.

     

Osmoconditioning and Ageing of Pepper Seeds During Storage

The effects of osmoconditioning on the germination at 15 and25 °C of pepper (Capsicum annuum L.) seeds were studiedover a 3-year period with respect to temperature of storage.Untreated seeds stored at 5 °C showed high germinabilitythroughout the entire storage period, whereas untreated seedsstored at 25 °C showed a progressive decline in germinability,especially when assayed at 15 °C. Seeds that had been osmoconditionedprior to storage retained a high level of germinability irrespectiveof either storage or germination temperatures. When seeds thathad been stored at 25 °C were osmoconditioned after storage,there was a significantly higher germinability (assayed at 15 °C) in comparison with the corresponding untreated seeds.Seeds that were osmoconditioned twice (prior to and after storage)germinated in a similar way to those that had been osmoconditionedonce only Lactuca saliva L., lettuce, Hordeum oulgare L., barley, seed storage, moisture content, relative humidity, water potential, temperature, oxygen     

Seed Dormancy,Seedling Establishment and Dynamics of the Soil Seed Bank of Stipa bungeana (Poaceae) on the Loess Plateau of Northwestern China

Studying seed dormancy and its consequent effect can provide important information for vegetation restoration and management. The present study investigated seed dormancy, seedling emergence and seed survival in the soil seed bank of Stipa bungeana, a grass species used in restoration of degraded land on the Loess Plateau in northwest China. Dormancy of fresh seeds was determined by incubation of seeds over a range of temperatures in both light and dark. Seed germination was evaluated after mechanical removal of palea and lemma (hulls), chemical scarification and dry storage. Fresh and one-year-stored seeds were sown in the field, and seedling emergence was monitored weekly for 8 weeks. Furthermore, seeds were buried at different soil depths, and then retrieved every 1 or 2 months to determine seed dormancy and seed viability in the laboratory. Fresh seeds (caryopses enclosed by palea and lemma) had non-deep physiological dormancy. Removal of palea and lemma, chemical scarification, dry storage (afterripening), gibberellin (GA₃) and potassium nitrate (KNO₃) significantly improved germination. Dormancy was completely released by removal of the hulls, but seeds on which hulls were put back to their original position germinated to only 46%. Pretreatment of seeds with a 30% NaOH solution for 60 min increased germination from 25% to 82%. Speed of seedling emergence from fresh seeds was significantly lower than that of seeds stored for 1 year. However, final percentage of seedling emergence did not differ significantly for seeds sown at depths of 0 and 1 cm. Most fresh seeds of S. bungeana buried in the field in early July either had germinated or lost viability by September. All seeds buried at a depth of 5 cm had lost viability after 5 months, whereas 12% and 4% seeds of those sown on the soil surface were viable after 5 and 12 months, respectively.     

After-Ripening in Festuca idahoensis Seeds: Adaptive Dormancy and Implications for Restoration

Festuca idahoensis (Idaho fescue) was a common native perennial bunchgrass in the sagebrush steppe of the western United States until the introductions of domestic livestock and alien plants. Restoration of Idaho fescue to degraded sites will likely involve reseeding, and one of the factors affecting reseeding success is germinability of the seeds employed. We investigated effects of after-ripening and storage temperature on germinability of Idaho fescue seeds collected from a central Oregon site. Six months of after-ripening were required before maximum germination was obtained. Storage of dry seeds at either room temperature (20°C) or at cooler, alternating temperatures (5/15°C) did not alter the rate at which dormancy was lost. Storage at the warmer temperature promoted rapid germination in seeds that had broken dormancy. Seed longevity varied greatly from year to year. Seeds produced in a very dry year had poorer germination and shorter longevity than seeds produced during a year with near normal precipitation. Because seed dispersal occurs in late July and early August for Idaho fescue in central Oregon, a six-month after-ripening requirement ensures that the greatest potential germination coincides with the spring period most likely to provide sufficient moisture for seedling establishment.