Dormancy-breaking requirements and level of morphophysiological dormancy (MPD) were determined for seeds of Ilex formosana and I. uraiensis from the subtropical region, and seeds of I. rotunda from both the subtropical and tropical regions of Taiwan. We hypothesized that some Ilex species would have deep simple MPD broken by warm stratification. Germination of seeds and embryo growth was monitored at 30/20, 25/15, 20/10, 15/5°C and at 25°C. Seeds were cold-stratified and then incubated at 25/15°C, and seeds treated with GA3 and GA4 were incubated at 25/15°C. Fresh seeds reached 50% germination after 11–45 weeks of warm stratification. Pre-treatment with GA increased germination percentages of I. formosana and I. rotunda (tropical) but not I. uraiensis and I. rotunda (subtropical), while cold stratification did not promote germination of either species but increased the germination rate of I. rotunda (tropical). Embryo length in seeds of all species increased ≥710% prior to root emergence, and growth occurred during warm stratification. The positive response to GA and relatively short time for beginning of germination and to reach 50% germination indicate non-deep simple MPD in seeds of I. formosana and I. rotunda (tropical). The negative response to GA and long time for beginning of germination and to reach 50% germination indicate deep simple MPD in seeds of I. uraiensis and I. rotunda (subtropical). Thus, in both the subtropical and tropical regions of Taiwan, the seeds of Ilex species have non-deep simple and deep simple MPD that are broken by warm stratification. Furthermore, GA treatment increases the germination rate and percentage of Ilex seeds with non-deep simple MPD, and cold stratification promotes the seed germination rate of Ilex species with non-deep simple MPD in tropical region.

Information about seed dormancy cycling and germination in relation to temperature and moisture conditions in the natural environment is important for the conservation and restoration of rare species, including Begonia guishanensis and Paraisometrum mileense, two sympatric perennial limestone (karst) species. Dry afterripening (DAR) and wet and dry (WD) cycles at 15/5 and 25/15°C as well as moist chilling (MC) at 15/5°C were used to mimic the natural environment at different times of the year. A field experiment was conducted to monitor seasonal changes in germination responses of the seeds. About 40–65% of B. guishanensis and 5% of P. mileense seeds were dormant at maturity. DAR at 25/15 and 15/5°C as well as MC and WD cycles at 15/5°C alleviated dormancy for B. guishanensis but not P. mileense, and WD cycles at 25/15°C induced a deeper conditional dormancy for both species. Seeds of B. guishanensis exhibited dormancy cycling in the field, with increased dormancy under natural WD cycles at relatively high temperatures during the transition from the dry to the wet season in April to May and decreased dormancy during the wet season from June to October. KNO3 mitigated the dormancy-inducing effect of both artificial and natural WD cycles at relatively high temperatures for B. guishanensis. The field experiment indicated that seeds of B. guishanensis may be able to form a persistent soil seed bank, while almost all seeds of P. mileense germinate at the beginning of the wet season in the field.

Common seepweed [Suaeda glauca (Bunge) Bunge] is a common salt-tolerant weed species distributed across the agricultural regions of northern China. It produces dimorphic seeds with different phenotypic characteristics and seed sizes. However, there is no information regarding the germination biology of these dimorphic seeds. Studies were conducted to evaluate the effects of ecological factors such as temperature, light, pH, osmotic stress, salt concentration, and planting depth on seed germination and seedling emergence. The results showed that brown seeds were nondormant, whereas black seeds had an intermediate physiological dormancy. The germination percentage of brown seeds was more than 80% at all temperature regimes and light conditions, but the optimum germination occurred at the cold thermoperiod of 20/10 C. In contrast, less than 6% of black seeds germinated at all temperature regimes and light conditions. Eight weeks of cold stratification did not break the dormancy of black seeds, whereas low concentrations of gibberellic acid (0.1 and 1.0 mM) significantly increased seed germination. Removal of the testa of black seeds also promoted germination and produced normal seedlings. Brown seeds showed moderate tolerance to salt stress, with 16% germination percentage at a salt concentration of 600 mM NaCl. The germination of brown seeds was 38% at an osmotic potential stress of −0.8 MPa; above that, no germination was obtained. Brown seeds germinated well in a wide pH range (4 to 10), with a germination percentage higher than 95%. Seedling emergence percentage was higher than 90% at burial depths of 0 to 2 cm, while germination percentage severely decreased for brown seeds with burial depths >2 cm, indicating that shallow tillage could be an effective measure to minimize seed germination. Information gathered from this study will help to develop an effective protocols for controlling S. glauca.

As a contribution to understanding the world biogeography of seed dormancy in the cosmopolitan genus Ilex, we studied seeds of I. argentina, I. brasiliensis, I. brevicuspis, I. dumosa, I. paraguariensis and I. theezans from the subtropical region of Argentina. We hypothesized that seeds of these species have non-deep simple morphophysiological dormancy (MPD). Effects of temperature, cold stratification and gibberellic acid (GA3) on seed germination and embryo growth were tested. Regardless of incubation temperature, little or no germination occurred for any species until ≥6 weeks. There was an up to 3-fold increase in embryo length to seed length (E:S) ratio before seeds germinated, and embryos grew only during warm-stratifying conditions. Seeds of I. brasiliensis, I. brevicuspis and I. theezans had non-deep simple MPD and germinated to ≥80% after 12, 24 and 16 weeks, respectively. Cold stratification increased germination of I. brasiliensis and I. brevicuspis, and GA3 increased the rate but not final germination percentage of I. brasiliensis and I. theezans. Fresh seeds of I. dumosa required 40 weeks of warm stratification to germinate to 53%, while those after-ripened for 2 months germinated to 81% after 30 weeks; this species has intermediate simple MPD. Seeds of I. argentina and I. paraguariensis germinated to 15 and 21%, respectively, after 40 weeks of warm stratification and did not after-ripen or respond to GA3; these seeds have deep simple MPD. This is the first report of intermediate and deep simple MPD that is broken by warm stratification, thereby increasing our knowledge of seed dormancy in Ilex and in subtropical regions.

Ferula ovina is a perennial Apiaceae with great medicinal and economic value. This study was conducted to better understand the dormancy and germination behaviour of its seeds. Experiments included temperature requirements for both embryo growth and germination under field and laboratory conditions, the effects of warm stratification, gibberellic acid (GA3), dry after-ripening, exogenous hydrogen peroxide (H2O2) and diphenyleneiodonium (DPI) on dormancy, localizing the accumulation of superoxide (O2−) and measuring endogenous contents of H2O2 in embryos during cold and warm stratification. Embryos were under-developed and did not germinate within one month at temperatures higher than 10°C. Among all treatments, cold stratification and exogenous H2O2 could break dormancy. However, the application of DPI reduced growth and the germination of the embryo at 3°C. During cold stratification, the embryonic axes elongated more than the cotyledons, which coincided with earlier production of O2− in the axes. Only these embryos could eventually complete growth and germinate. Moreover, such asymmetric growth between the axes and cotyledons was also observed when seeds were treated with exogenous H2O2. On the other hand, both axes and cotyledons displayed the same growth over treatments with warm stratification and DPI. Overall, seeds of F. ovina exhibit the characteristics of deep complex morphophysiological dormancy. Moreover, the embryos solely require cold to complete growth and to germinate, and this process seems to be mediated by reactive oxygen species. Under natural conditions, seeds germinate during winter in cold soil, and shoots emerge in spring.

Abies cephalonica cone and seed morphometric characteristics as well as seed germination behaviour were investigated during an 8-year-long diachronic study (2007–2015). The research was carried out in Parnitha National Park, in the part of this Greek endemic, silver fir population that was spared from an unprecedented wildfire (2007). A statistically significant interannual and among-tree variation of cone traits has been identified, except for cone diameter. Cone length is correlated to the number of seeds per cone, while the percentage of empty seeds has been consistently high, with extreme values of 29.3 and 81.8% in a masting (2015) and lean crop (2009) year, respectively. There is also a considerable proportion of dead (including infected) and non-germinated seeds, and the eventual germinable fraction is well below 25% with spikes in masting years (39.4 and 60.9% in 2010 and 2015, respectively). Untreated seeds have been tested at a wide range of constant and alternating temperatures and germination is completed within 4–5 weeks at T ≥ 15°C and ca 15 weeks at 5–10°C. A chilling pretreatment of 4–8 weeks (at 2–4°C) concludes germination at 15–20°C within 2 weeks. A significant white light requirement has been observed for untreated seeds at 15–20°C, while germination was light indifferent at lower or higher temperatures. Data obtained in this study confirm the present, field seed germination during springtime; we may also predict an earlier germination (late autumn to mid-winter) in forest gaps, under the predicted, warmer conditions in the future.

Little is known about the biology and control of hophornbeam copperleaf, a weed of increasing importance in the Midwest. More than 2 wk of cold stratification and a 0.2% KNO3 solution increased germination of hophornbeam copperleaf. Germination at constant 30 C was 47% and alternating 30/20 C was 65%. Scarification did not increase hophornbeam copperleaf germination. Within the first 600 growing degree days after soybean planting, plant height, leaf area, and dry matter accumulation of hophornbeam copperleaf grown in soybean and alone were similar. Subsequently, leaf area and dry matter accumulation of hophornbeam copperleaf grown alone were greater than of those grown in soybean. In contrast, plant height of hophornbeam copperleaf grown in soybean was greater than when grown alone. Hophornbeam copperleaf grown alone produced up to 12 510 seeds/plant, whereas hophornbeam copperleaf grown with soybean produced 980 seeds/plant. Of 13 postemergent herbicides evaluated on hophornbeam copperleaf in soybean, only lactofen, acifluorfen, and fomesafen controlled 80% or more. Lactofen at 210 g ai/ha consistently controlled more than 95% of the hophornbeam copperleaf.

Mechanical scarification of burcucumber (Sicyos angulatus L.) seeds resulted in increased water absorption and germination. Burcucumber germination occurred at temperatures ranging from 15 to 35 C with optimum germination occurring from 20 to 30 C. Scarified burcucumber seeds were more sensitive to simulated moisture stress than were either soybean [Glycine max (L.) Merr. ‘Williams’] or corn [Zea mays L. ‘Pioneer Brand 3369A’]. Regardless of osmotic potential, intact burcucumber seeds did not germinate; scarified seeds germinated at osmotic potentials to −6 bars. Cold stratification at 4 C for 18 weeks modified seedcoat permeability so that 11% of non-scarified burcucumber seeds germinated. Increasing depth of planting decreased emergence with limited emergence occurring at depths of 15 and 16 cm in field and growth chamber studies, respectively.

Ripgut brome is a difficult weed to manage in cereal crops of southern Australia because only a few herbicides can provide effective control in cereals. Knowledge of seed-dormancy mechanisms, germination ecology, and emergence behavior in the field could facilitate development of effective weed control programs for this weed species. Ripgut brome populations from cropping fields were found to possess much longer seed dormancy than that reported previously in the literature. Furthermore, some ripgut brome populations from cropping fields showed longer seed dormancy than those collected from adjacent noncropped fence lines. For example, all seeds of one of the populations from the fence line (SA-1F) germinated at 3 mo after maturity, whereas seeds from the cropping field at the same site (SA-1C) showed little germination (< 3%) even at 8 mo after maturity. These highly dormant ripgut brome populations from cropping fields were responsive to cold stratification, with germination increasing significantly after 2 to 14 d of exposure. Germination of dormant ripgut brome populations increased with addition of gibberellic acid (0.001 M GA3), particularly when lemma and palea had been removed. Ripgut brome populations from cropping fields (VIC-2C and SA-1C) showed strong inhibition of seed germination when exposed to light. These differences in seed dormancy among ripgut brome populations were also expressed in seedling emergence pattern in the field. The nondormant populations collected from fence lines showed high seedling establishment (> 80%) during autumn, which coincided with the planting time of winter crops in southern Australia. In contrast, five populations from cropping fields showed much lower seedling establishment (3 to 17%) before the time of crop planting. Delayed seedling establishment in populations from cropping fields could lead to less effective preseeding weed control and higher weed infestations in field crops. Results of this study also showed that the seedbank of these highly dormant ripgut brome populations can readily persist from one year to the next. Effective management of ripgut brome populations with long seed dormancy and increased seedbank persistence would require a major change in cropping systems used by the growers in southern Australia.

Garlic mustard is among the most important invasive weeds of North American eastern deciduous forests. Investigations of the mechanisms that enable its success as an invader require a simple method to propagate this weed in the laboratory and the greenhouse; we develop such a method in this study. Cold treatment (24-h dark cycle; maximum 6 C, minimum −1 C) for at least 100 d on a moist organic mix, followed by incubation at temperatures approximating spring (maximum 15 C, minimum 6 C), results in close to 100% germination. The information presented here will be valuable in studies requiring a steady supply of garlic mustard plants for experimentation and for the mass rearing of biological control agents.

Laboratory experiments were conducted to determine the effects of temperature, light, cold stratification, dry storage, solution pH, solution osmotic potential, and planting depth on germination and emergence of dame's rocket. Maximal germination (> 80%) of fresh seeds occurred at alternating temperatures ≥ 25/15 C in both alternating light/dark and continuous darkness. However, < 10% of seeds germinated at or below 20/10 C, with lower germination in the presence of light than in darkness. Cold stratification at 4 C for 4 to 16 wk enhanced germination at low alternating temperatures (≤ 20/10 C), but depressed germination at warm temperature regimes (≥ 25/15 C). After 1 yr of dry storage (after-ripening), germination exceeded 94% and did not differ significantly among temperature regimes. Germination exceeded 60% in solutions with pH 3 to 10. Germination was reduced below 50% in solutions with osmotic potentials below −0.6 MPa. Percent emergence was greater than 56% at burial depths in soil of 0 to 5 cm, with maximal emergence (93 to 99%) at 0 to 2 cm. Dame's rocket seeds possess non-deep physiological dormancy at maturity, but when dormancy is alleviated, the seeds are capable of germinating in a variety of climatic and edaphic conditions.

Weedy barley species have emerged as important weeds in southern Australia, where they can be particularly difficult to control in cereal crops. Knowledge of seed dormancy mechanisms, germination ecology, and recruitment behavior in the field would facilitate development of effective weed-control programs for these weed species. Based on somatic chromosome number, smooth barley was identified as the species infesting all the sites sampled in South Australia. Smooth barley populations from cropping fields and noncrop habitats showed large differences in their pattern of dormancy loss. Noncrop populations (EP2, EP3, and MN2) rapidly lost dormancy during dry after-ripening and showed 70 to 95% germination at 3 mo after maturity. Five populations collected from cropping fields (EP1, EP4, EP5, MN1, and MN3), on the other hand, showed < 30% germination, even at 8 mo after maturity, when germination was assessed at 20/12 C day/night temperatures. These dormant, smooth barley populations from cropping fields were found to be highly responsive to cold stratification, with germination increasing in response to the duration of the treatment. Germination of dormant, smooth barley populations increased with the addition of gibberellic acid (0.001 M GA3), but only when lemma and palea had been removed. Recruitment behavior of smooth barley in the field was influenced by the population and the tillage system. A nondormant population, collected from a long-term pasture (MN2), showed high seedling emergence (> 90%) during autumn, which was well before planting of the winter crop (lentil). In contrast, the other three populations sampled from cropping fields showed very little seedling establishment (< 10%) before crop planting, which would make them difficult to control in cereals because there are no selective herbicides available for the control of weedy barley species. There was a significant seeding system by emergence time interaction (P < 0.001), which was reflected in greater in-crop, smooth barley plant densities under zero-till than under conventional tillage and no-till systems.

Spreading orach is an annual weed that colonizes roadsides, field edges, and increasingly, no-till agricultural fields. It produces dimorphic seeds with different levels of physiological dormancy, but little is known about the germination ecology of the two seed types. Field and controlled-environment studies were conducted to determine seed responses to light and stratification, the pattern of seedling emergence in the field, and the effect of soil water content on the length of cold stratification required to break dormancy for each seed type. The large, brown seeds have three times the mass of the smaller, black seeds, primarily because of a larger embryo, but have a thinner seed coat. Germination of brown and black seeds in petri dishes was 98 and 90%, respectively, after stratification for 3 mo at 5 C, whereas germination of unstratified seeds was 19 and 12%, respectively. Light stimulated germination of both stratified and unstratified black seeds but did not increase germination in stratified brown seeds. Up to 40% of brown seeds germinated in situ during stratification, compared with only 2% for black seeds. Germination in petri dishes and emergence in the field were more rapid for brown seeds than for black seeds. Maximum germination of black seeds occurred after stratification for 2 or 3 mo at 5 C on soil that was waterlogged (pore-water matric potential, ψ = 0 kPa), wet (ψ = −0.38 kPa), or at field capacity (ψ = −10 kPa). For shorter periods of stratification, total germination and germination rate of black seeds declined as soil water content decreased from waterlogged to dry (ψ = −500 kPa). Seed dimorphism in spreading orach may provide a mechanism to enhance survival in uncertain or variable habitats such as disturbed agricultural fields.

Knowledge about the hormonal control of grain dormancy and dormancy loss is essential in wheat, because low grain dormancy at maturity is associated with the problem of pre-harvest sprouting (PHS) when cool and rainy conditions occur before harvest. Low GA (gibberellin A) hormone sensitivity and high ABA (abscisic acid) sensitivity were associated with higher wheat grain dormancy and PHS tolerance. Grains of two PHS-tolerant cultivars were very dormant at maturity, and insensitive to GA stimulation of germination. More PHS-susceptible cultivars were less sensitive to ABA inhibition of germination, and were either more GA sensitive or germinated efficiently without GA at maturity. As grain dormancy was lost through dry afterripening or cold imbibition, grains first gained GA sensitivity and then lost ABA sensitivity. These changes in GA and ABA sensitivity can serve as landmarks defining stages of dormancy loss that cannot be discerned without hormone treatment. These dormancy stages can be used to compare different cultivars, seed lots and studies. Previous work showed that wheat afterripening is associated with decreasing ABA levels in imbibing seeds. Wheat grain dormancy loss through cold imbibition also led to decreased endogenous ABA levels, suggesting that reduced ABA signalling is a general mechanism triggering dormancy loss.

Temperate wetland species often require light and warm temperatures for seed germination. However, recent studies indicate that species which specialize on permanently saturated wetlands that are maintained by groundwater discharge (fens, seeps and mountain springs), rather than wetlands with surface-water-driven hydrologic regimes, diverge from the typical wetland germination niche by germinating at cool temperatures and lacking photoblastic seeds. We conducted laboratory experiments that manipulated stratification conditions (non-stratified versus cold stratification in light and darkness), thermal regime (15/6, 25/15 and 35/20°C), and light (14 h photoperiod versus continuous darkness) to test whether seeds of the North American calcareous fen specialist Parnassia grandifolia diverged from the typical temperate wetland germination niche. After 30 d, fresh seeds were conditionally dormant and could only germinate to high percentages in light at 25/15°C. During 16 weeks of incubation, non-stratified seeds germinated to low percentages ( < 40%) at all thermal regimes in darkness. In contrast, cold-stratified seeds germinated to high percentages in both light and darkness at all thermal regimes, although germination was incomplete (no cotyledon emergence) at 35/20°C. Further, seeds did not require light during cold stratification to germinate to high percentages when incubated in light or darkness. Thus, seeds diverged from the typical temperate wetland germination syndrome in lacking a light and warm temperature requirement for germination. Our results reinforce previous work from European fens and Mediterranean wetlands. This indicates that multiple germination strategies are found in fen wetlands that are maintained by the continuous or near-continuous discharge of cool groundwater.

Although mature seeds of the monogeneric conifer family Cephalotaxaceae sensu stricto have underdeveloped embryos, no definitive studies have been done to classify dormancy in this family. Our primary purpose was to determine the kind of dormancy in seeds of Cephalotaxus wilsoniana and to put the results into a broad phylogenetic context for gymnosperms. The species is of horticultural and medicinal value, and information is needed on how to propagate it efficiently from seeds. Embryo growth and germination were monitored for seeds at warm, cold and warm plus cold temperatures, and germination was monitored for seeds subjected to: (1) cold →  warm →  cold →  warm; and (2) warm →  cold →  warm →  cold →  warm temperature sequences. The effects of gibberellic acids GA3 and GA4 were tested on radicle emergence in ungerminated seeds and on shoot emergence in root-emerged seeds. Germination was promoted by ≥ 36 weeks of warm stratification followed by ≥ 8 weeks of cold stratification, but only if seeds were returned to high temperatures. The underdeveloped embryo must increase in length by >120% before the radicle emerges. Neither GA3 nor GA4 was effective in promoting radicle emergence; however, both plant growth regulators increased rate (but not percentage) of shoot emergence in root-emerged seeds. We conclude that seeds of C. wilsoniana have the deep simple level of morphophysiological dormancy (MPD), C1b-C3-B1b; thus, warm stratification followed by cold stratification and then warm-temperature incubation are required for germination. In gymnosperms, MPD is known in cycads, Ginkgo and now in three families of conifers.

Seeds of Aconitum napellus subsp. castellanum were physiologically dormant at maturity in early autumn, with underdeveloped embryos. Thus they have morphophysiological dormancy (MPD). Embryos in fresh seeds were on average 1.01 mm long, and they had to grow to 3.60 mm before radicle emergence. Cold stratification at 5°C for 5 months with light enhanced the mean embryo length to 2.73 mm (SE = 0.13) and seed germination to 20%. However, with higher temperatures (15/4, 20/7, 25/10, 28/14 and 32/18°C) embryo growth was small, with no seeds germinating. Optimal germination was achieved after 4 months of cold stratification at 5°C followed by incubation at 20/7°C for 1 month with light, when germination ranged between 70 and 79%, depending on seed age, locality and year of collection. Cold stratification could be substituted by the application of GA3 solution, since mean embryo length in seeds incubated at 25/10°C for 1 month with light was 3.52 mm and the germination was 80%. Since cold stratification was the only requirement for the loss of MPD, the longest embryo growth occurred during this treatment, and GA3 promoted MPD loss, we concluded that A. napellus seeds have intermediate complex MPD. Germination was higher in 4-month stored than in freshly matured seeds. A pronounced variability in germinative patterns at inter-annual and inter-population level was recorded.

Solidago shortii is endemic to a small area in northcentral Kentucky (USA), whereas two of its sympatric congeners, S. altissima and S. nemoralis, are geographically widespread. Seeds (achenes) of S. shortii (0.370 mg) are significantly larger (PLSD, P=0.05) than those of S. altissima (0.070 mg) and S. nemoralis (0.068 mg). Germination percentages of freshly-matured seeds of the three Solidago species collected in November 1991, 1992 and 1994 were 0–2% in light at 15/6°C, 1–37% at 20/10°C, 9–56% at 25/15°C and 10–85% at 30/15 and 35/20°C. Stratification increased the percentage and rate of germination and decreased the time to the onset of germination (measured by Timson's index only at 20/10°C in light) in the three species. Following 12 weeks of cold stratification in light, seeds of the three species germinated to 72–100% in the light and to 22–100% in darkness over the range of thermoperiods; those cold-stratified in darkness germinated to 39–100% in light. Freshly-matured seeds of S. altissima and of S. nemoralis germinated to 0–4% in darkness, whereas those cold-stratified for 12 weeks in darkness germinated to 0–28% in darkness. On the other hand, freshly-matured and cold-stratified (in darkness) seeds of S. shortii germinated to 0–13 and 13–73%, respectively, in darkness. Under near-natural temperatures in a glasshouse without temperature control, germination of the three species peaked in March. Thus, the primary difference in dormancy-breaking and germination requirements of the three species is that the endemic germinates to a much higher percentage in darkness than its two congeners. Seeds of S. shortii do not have any special dormancy-breaking or germination requirements that could not be fulfilled outside its present-day geographic range.

While red rice (Oryza sativa L.) can remain dormant and viable for many years when fully imbibed, the environmental factors that stimulate germination or induce secondary dormancy in the field have not been characterized. In this study, the interactions between the extent of dry-afterripening and germination temperature have been evaluated as possible factors. Red rice dispersal units (florets) were afterripened for 0–10 weeks at 30°C and incubated in water at 1, 5, 15, 20, 25, 30 and 35°C for 2 weeks; then, all the ungerminated florets were transferred to 30°C for two additional weeks. Germination at the end of each of the two sequential treatments was compared to define both the effect of differing temperatures on germination (first treatment), and the effect of these temperatures on subsequent germination at the optimum temperature (30°C, second treatment). In afterripening red rice, the opening of the temperature window for germination begins at 25–35°C. Fully dormant florets acquired the ability to germinate ≥ 90% at 30°C after 4 weeks of dry-afterripening. However, imbibing florets for 2 weeks at 15°C followed by 2 weeks at 30°C, yielded suboptimal germination and induced a degree of secondary dormancy, dependent upon the extent of previous dry-afterripening. Cold stratification (1°C) had a consistent promotive effect on the subsequent germination, particularly when preceded by 1–2 weeks of dry-afterripening at 30°C. To monitor the effects of germination temperature, median afterripening time was utilized as a relative dormancy index, and changes in this index have been interpreted as an overlapping of germination and the temperature-induced changes in the dormancy status. Field weather data suggested that low-temperature stratification may be a germination trigger in the field, even in southern Louisiana, and this merits further investigation in studies of soil-buried seeds.

Seed salinity tolerance and dormancy play important roles in germination behaviour. The effects of NaCl concentration and different dormancy-breaking treatments on germination were determined for six species growing on the coasts of the Baltic Sea or the Gulf of Riga: Juncus balticus, Triglochin maritima, Triglochin palustre, Anthyllis maritima, Linaria vulgaris and Linaria loeselii. Germination percentages were significantly reduced at NaCl concentrations >100 mM. Germination of J. balticus, T. maritima and T. palustre, but not that of A. maritima and L. vulgaris, recovered after seeds were rinsed with distilled water. Seeds of J. balticus were non-dormant; those of A. maritima had physical dormancy; and those of T. palustre, T. maritima, L. loeselii and L. vulgaris had non-deep to intermediate physiological dormancy, which was broken by cold stratification or gibberellic acid. The seeds of plants growing in habitats periodically exposed to sea water (coastal meadows) were characterized by greater salinity tolerance than seeds of plants growing in habitats less exposed to sea water (dunes).