Germination of Basidiospores of Agaricus bisporus

The type of dormancy and conditions necessary for germination of Agaricus bisporus basidiospores were studied. Basidiospores failed to germinate on starvation agar and required the presence of carbon and nitrogen sources (asparagine and/or glucose) in the medium. Upon 3-week storage, basidiospores germinated after 4–5 days. Heat shock (20 min at 45°C) and decreased temperature facilitated activation of germination. Heterocyclic compounds stimulating germination of endogenously dormant spores, such as furfural, failed to activate germination. The data obtained suggested an endogenous dormancy of A. bisporus basidiospores differing from zygospores of Mucorales. Basidiospores contained 17–19% lipids with a composition of fatty acids differing from those of the pileus and stipe of the fruiting body. The soluble carbohydrates of the cytosol amounted to 12% dry spore weight and consisted of mannitol (74%) and trehalose (26%). Unlike basidiospores stored at 2°C, basidiospores stored for 5 months at 20°C lost their ability to germinate, which correlated with a decrease in the content of trehalose.     

The changing window of conditions that promotes germination of two fire ephemerals, Actinotus leucocephalus (Apiaceae) and Tersonia cyathiflora (Gyrostemonaceae)

BACKGROUND AND AIMS: Following a period of burial, more Actinotus leucocephalus (Apiaceae) and Tersonia cyathiflora (Gyrostemonaceae) seeds germinate in smoke water. The main aim of this study was to determine whether these fire-ephemeral seeds exhibit annual dormancy cycling during burial. This study also aimed to determine the effect of dormancy alleviation on the range of light and temperature conditions at which seeds germinate, and the possible factors driving changes in seed dormancy during burial. METHODS: Seeds were collected in summer, buried in soil in mesh bags in autumn and exhumed every 6 months for 24 months. Germination of exhumed and laboratory-stored (15 degrees C) seeds was assessed at 20 degrees C in water or smoke water. Germination response to light or dark conditions, incubation temperature (10, 15, 20, 25 and 30 degrees C), nitrate and gibberellic acid were also examined following burial or laboratory storage for 24 months. In the laboratory seeds were also stored at various temperatures (5, 15, 37 and 20/50 degrees C) for 1, 2 and 3 months followed by germination testing in water or smoke water. KEY RESULTS: The two species exhibited dormancy cycling during soil burial, producing low levels of germination in response to smoke water when exhumed in spring and high levels of germination in autumn. In autumn, seeds germinated in both light and dark and at a broader range of temperatures than did laboratory-stored seeds, and some Actinotus leucocephalus seeds also germinated in water alone. Dormancy release of Actinotus leucocephalus was slow during dry storage at 15 degrees C and more rapid at higher temperatures (37 and 20/50 degrees C); weekly wet/dry cycles further accelerated the rate of dormancy release. Cold stratification (5 degrees C) induced secondary dormancy. By contrast, no Tersonia cyathiflora seeds germinated following any of the laboratory storage treatments. CONCLUSIONS: Temperature and moisture influence dormancy cycling in Actinotus leucocephalus seeds. These factors alone did not simulate dormancy cycling of Tersonia cyathiflora seeds under the conditions tested.     

Involvement of ABA in induction of secondary dormancy in barley (Hordeum vulgare L.) seeds

At harvest, barley seeds are dormant because their germination is difficult above 20 degrees C. Incubation of primary dormant seeds at 30 degrees C, a temperature at which they do not germinate, results in a loss of their ability to germinate at 20 degrees C. This phenomenon which corresponds to an induction of a secondary dormancy is already observed after a pre-treatment at 30 degrees C as short as 4-6 h, and is optimal after 24-48 h. It is associated with maintenance of a high level of embryo ABA content during seed incubation at 30 degrees C, and after seed transfer at 20 degrees C, while ABA content decreases rapidly in embryos of primary dormant seeds placed directly at 20 degrees C. Induction of secondary dormancy also results in an increase in embryo responsiveness to ABA at 20 degrees C. Application of ABA during seed treatment at 30 degrees C has no significant additive effect on the further germination at 20 degrees C. In contrast, incubation of primary dormant seeds at 20 degrees C for 48 and 72 h in the presence of ABA inhibits further germination on water similarly to 24-48 h incubation at 30 degrees C. However fluridone, an inhibitor of ABA synthesis, applied during incubation of the grains at 30 degrees C has only a slight effect on ABA content and secondary dormancy. Expression of genes involved in ABA metabolism (HvABA8'OH-1, HvNCED1 and HvNCED2) was studied in relation to the expression of primary and secondary dormancies. The results presented suggest a specific role for HvNCED1 and HvNCED2 in regulation of ABA synthesis in secondary seed dormancy.     

Relationships between seed germinability of Spergularia marina (Caryophyllaceae) and the formation of zonal communities in an inland salt marsh

BACKGROUND AND AIMS: The formation of zonal communities may be attributed to differences in germination across the community and to timing of germination of seeds present in the seed bank. Our goals were two-fold: (1) to assess the annual germination pattern of Spergularia marina; and (2) to determine whether germination of S. marina differed across zonal communities. METHODS: Fresh seeds were buried in an experimental garden in polyester bags. Bags were harvested monthly for 1 year and exposed to differing 12 h/12 h temperature regimes (5/15 degrees C, 5/25 degrees C, 15/25 degrees C and 20/35 degrees C) with a 12 h dark/12 h light photoperiod. Replicate seeds were exposed to 24 h dark. Seeds were also placed in different zonal communities to assess germinability in the field. KEY RESULTS: Spergularia marina has a primary physiological dormancy. Conditional dormancy occurs from December to May and non-dormancy from June to November. Field germination initiates in the spring when temperatures are cool and salinity is low due to flooding, and ceases in the summer when temperatures exceed germination requirements. Spergularia marina has a light requirement for germination. CONCLUSIONS: If seeds become buried in the field or are light inhibited by Phragmites australis, they will remain dormant until they receive an adequate amount of light for germination. Since S. marina can germinate across all zones in a salt-marsh community, the formation of zonal communities is not determined at the germination stage, but at some later stage of development.     

Low Temperature Storage of Caryopses of Triticum durum: Viability and Longevity

Germination of Triticum durum Desf. ‘Cappelli’ caryopsesstored in hermetically-sealed containers at 10°C or -20°Cwas analysed. Caryopses were maintained in laboratory conditions(20 ± 4°C) prior to controlled storage, which began5 d, 240 d and 7 years after harvesting. In addition, after9 years of storage, one 10°C stored batch of caryopses andtwo -20°C stored batches were returned to laboratory conditions.Germination over time and seed longevity were investigated.Results showed that: (1) under laboratory conditions, caryopsesin relative (primary) dormancy at the beginning of storage hadlost dormancy after 45 d and germination ability was lost bythe end of year 7. (2) When stored at 10°C, relative dormancyin caryopses was lost within 1 year, but 100% germination abilitywas retained after 23 years of storage. (3) When stored at -20°C,caryopses that were dormant at the beginning of storage (5 dafter harvesting) maintained this condition for 23 years whilecaryopses which were placed in storage 240 d after harvesting,when relative dormancy had already been broken, maintained 100%germination ability. Caryopses returned to laboratory conditionsafter 9 years of storage at 10°C or -20°C showed thesame trend as caryopses maintained exclusively in laboratoryconditions since the time of harvesting. Caryopses removed from-20°C overcame relative dormancy in 50 d and maintainedgermination ability for roughly 7 years, while those removedfrom 10°C lost the ability to germinate by the end of thefifth year. Copyright 2000 Annals of Botany Company Germination, longevity, low-temperature-storage, Triticum durum, viability     

Patterns of seed after-ripening in Bromus tectorum L

For grass seeds that lose dormancy through after ripening indry storage, the probability of germination following a particularwetting event can be predicted only if the relationship betweenstorage temperature and change in after-ripening status is known.This study examined patterns of seed dormancy loss in Bromustectorum L., quantifying changes in germination percentage,speed, and uniformity through time. Seed collections from threesemi-arid habitats were stored at temperatures from 10–40C. At monthly intervals, subsamples were incubated at 5/15,10/20, 15/25, and 20/30 C. For recently harvested seeds, germinationpercentage, mean germination time, and days between 10% and90% of total germination (D90–D10) ranged from 1–75%,10–24 d, and 10–20 d, respectively. Recently harvestedseeds were generally most dormant, slowest to germinate andleast uniform at high incubation temperatures. In contrast,after ripened seeds for all collections had nearly 100% germination,mean germination times <5 d, and D90–D10 values <5d. Three indices were used to characterize after-ripening ratesfor each seedlot at each incubation temperature. The mean dormancyperiod, the mean rate index, and the mean uniformity index definedthe storage period required for seedlots to become half as dormantas at harvest, to progress half-way to the fastest speed, andto progress half-way to the greatest uniformity, respectively.Seeds required longer storage to germinate uniformly than togerminate completely or quickly, because germination time-coursecurves for incompletely after-ripened seeds were positivelyskewed rather than sigmoidal. Mathematically, the three indiceswere described as negative exponential functions of storagetemperature, which suggests that after-ripening is likely completedin late summer or early autumn regardless of summer conditions. Key words: Seed dormancy, germination timing     

PHYSIOLOGICAL ECOLOGY OF GERMINATION OF VIOLA RAFINESQUII

Seeds of the winter annual Viola rafinesquii Greene exhibit true dormancy at the time of maturity and dispersal in mid to late spring. During the summer rest period the seeds pass from a state of true dormancy to one of relative dormancy and finally to what may be called a state of complete nondormancy. As the seeds enter relative dormancy they will germinate mostly at relatively low temperatures (10, 15, 15/6, and 20/10 C), but as after-ripening continues they gain the ability also to germinate at higher temperatures (20, 25, and 30/15 C). During June, July, and August seeds will not germinate at field temperatures even if kept continuously moist. But by September and October seeds may germinate to high percentages over a wide range of temperatures, including September and October field temperatures. This pattern of germination responses, involving breaking of true dormancy and widening of the temperature range for germination during relative dormancy, appears to be an adaptation of the species to a hot, dry season. Seeds of V. rafinesquii stored on continuously wet soil (field capacity) or on soil that was alternately wet and dried during the summer did not after-ripen at low temperatures (10, 15, 15/6, and 20/10 C) but did after-ripen fully at high temperatures (20, 25, 30/15, and 35/20 C). Thus, the high temperatures that V. rafinesquii “avoids” by passing the summer in the dormant seed stage actually are required to break seed dormancy and, therefore, are essential for completion of its life cycle.     

Effects of long-term storage at different temperatures on conidia of Botrytis cinerea Pers.: Fr.

Survival of Botrytis cinerea conidia was studied after storage without pretreatments at different temperatures (-80 degrees C, -20 degrees C, 4 degrees C and 21 degrees C). Germination tests performed during 3 years showed that viability at 21 degrees C was completely lost after 1 month. Conidia stored for 30 months at -80 degrees C, -20 degrees C and 4 degrees C were able to germinate, respectively, at 79%, 8% and 0.2%. Changes in adenylate level, energy charge and respiration (O(2) consumption) made on each set of conidia were correlated to the germination rate. The 30-month-old stored conidia showed differences in pathogenicity tests on apples. While the pathogenic aggressiveness of conidia stored at -80 degrees C was almost the same as for fresh conidia, it decreased with increasing temperature of storage. An ultrastructural study made on conidia stored for 30 months at -80 degrees C has shown the emergence of a new wall layer in a retraction zone of the cytoplasm by comparison to fresh conidia. However, the integrity of the cytoplasmic content was maintained. The effects of low temperature storage, maintenance of cell integrity and pathogenicity of conidia of B. cinerea are discussed.     

EFFECT OF STRATIFICATION TEMPERATURE AND GERMINATION TEMPERATURE ON GERMINATION AND THE INDUCTION OF SECONDARY DORMANCY IN COMMON RAGWEED SEEDS

Stratification of common ragweed (Ambrosia artemisiifolia) seeds at 4 C was most successful for breaking dormancy, whereas -5 C was least effective and 10 C was intermediate. Germination in the light exceeded that in the dark at all stratification and germination temperatures. The optimum temperatures for germination in the light were 10/20, 15/25, and 20/30. Maximum germination in the dark occurred at 20/30 C for seeds stratified at 4 and 10 C but the optimum temperatures for seeds stratified at -5 C were 10/20, 15/25, and 20/30. Seeds stratified at -5 and 10 C germinated best after 15 weeks of stratification, whereas 12 weeks of stratification at 4 C resulted in maximum germination. Secondary dormancy was induced in seeds which did not germinate in the dark. This was affected by stratification temperature and duration and germination temperature. The ecological significance of these germination characteristics is discussed.     

Seed dormancy and germination of the European Chaerophyllum temulum (Apiaceae), a member of a trans-Atlantic genus

BACKGROUND AND AIMS: The European Chaerophyllum temulum and two North American Chaerophyllum species have a trans-Atlantic disjunct distribution. This work aimed to resolve requirements for dormancy break and germination of C. temulum seeds and to compare dormancy traits with those of the two North American congeners. METHODS: Phenology of germination and embryo growth was studied by regularly exhuming seeds sown in natural conditions. Temperature requirements for embryo growth, breaking of dormancy and germination were determined by incubating seeds under controlled laboratory conditions. Additionally the effect of GA(3) on germination was tested to determine the specific dormancy type. KEY RESULTS: In natural conditions, embryo growth starts in early winter. Seedlings emerge in late winter shortly after the embryos reached the critical ratio for embryo length to seed length (E : S) of approx. 0.95. Growth of the embryo only occurs during a prolonged incubation period at 5 degrees C. After stratification at 5 degrees C, which breaks physiological and morphological dormancy, seeds can germinate at a wide range of temperatures. GA(3) did not substitute for cold stratification in seeds placed at 23 degrees C. CONCLUSIONS: Chaerophyllum temulum has deep complex morphophysiological dormancy. This dormancy type differs considerably from that of the two North American congeners.     

Mouse sperm desiccated and stored in trehalose medium without freezing

Mouse sperm with and without trehalose were desiccated under nitrogen gas and stored at 4 degrees C and 22 degrees C. After rehydration, sperm were injected into oocytes using intracytoplasmic sperm injection and embryonic development was followed. Sperm were dried for 5.0, 6.25, or 7.5 min, stored at 22 degrees C for 1 wk with and without trehalose. The percentages of blastocysts that developed from sperm with trehalose were 51%, 31%, and 20%, respectively, which was significantly higher than sperm without trehalose (10%, 3%, and 5%, respectively). Desiccation and storage in medium with trehalose significantly increased sperm developmental potential compared to medium without trehalose. Sperm dried for 5 min produced more blastocysts than sperm dried for 6.25 or 7.5 min. When sperm were dried in trehalose for 5 min and stored for 1 wk, 2 wk, 1 mo, or 3 mo at 4 degrees C, the percentages of blastocysts were 73%, 84%, 63%, and 39%; whereas those stored at 22 degrees C for 1 wk, 2 wk, or 1 mo were significantly lower (53%, 17%, and 6%, respectively). Embryos from sperm partially desiccated in trehalose for 5 min and stored at 4 degrees C for 1 or 3 mo were transferred to 10 pseudopregnant recipients. Implantation rates were 81% and 48%; live fetuses were 26% and 5%, respectively. One of the recipients delivered three live fetuses. The results show that trehalose has a significant beneficial effect in preserving the developmental potential of mouse sperm following partial desiccation and storage at temperatures above freezing.     

Deep and intermediate complex morphophysiological dormancy in seeds of Ferula gummosa (Apiaceae)

We tested the hypothesis that seeds of the monocarpic perennial Ferula gummosa from the Mediterranean area and central Asia have deep complex morphophysiological dormancy. We determined the water permeability of seeds, embryo morphology, temperature requirements for embryo growth and seed germination and responses of seeds to warm and cold stratification and to different concentrations of GA₃. The embryo has differentiated organs, but it is small (underdeveloped) and must grow inside the seed, reaching a critical embryo length, seed length ratio of 0.65–0.7, before the seed can germinate. Seeds required 9 weeks of cold stratification at <10°C for embryo growth, dormancy break and germination to occur. Thus, seeds have morphophysiological dormancy (MPD). Furthermore, GA₃ improved the germination percentage and rate at 5°C and promoted 20 and 5% germination of seeds incubated at 15 and 20°C, respectively. Thus, about 20% of the seeds had intermediate complex MPD. For the other seeds in the seed lot, cold stratification (5°C) was the only requirement for dormancy break and germination and GA₃ could not substitute for cold stratification. Thus, about 80% of the seeds had deep complex MPD.     

Storage of Resting Spores of the Gypsy Moth Fungal Pathogen, Entomophaga maimaiga

The fungal pathogen, Entomophaga maimaiga causes epizootics in populations of the important North American forest defoliator gypsy moth ( Lymantria dispar ). Increasing use of this fungus for biological control is dependent on our ability to produce and manipulate the long-lived overwintering resting spores (azygospores). E. maimaiga resting spores undergo obligate dormancy before germination so we investigated conditions required for survival during dormancy as well as the dynamics of subsequent germination. After formation in the field during summer, resting spores were stored under various moisture levels, temperatures, and with and without soil in the laboratory and field. The following spring, for samples maintained in the field, germination was greatest among resting spores stored in plastic bags containing either moistened paper towels or sterile soil. Resting spores did not require light during storage to subsequently germinate. In the laboratory, only resting spores maintained with either sterile or unsterilized soil at 4°C (but not at 20 or -20°C) germinated the following spring, but at a much lower percentage than most field treatments. To further investigate the effects of relative humidity (RH) during storage, field-collected resting spores were placed at a range of humidities at 4°C. After 9.5 months, resting spore germination was highest at 58% RH and no resting spores stored at 88 or 100% RH germinated. To evaluate the dynamics of infections initiated by resting spores after storage, gypsy moth larvae were exposed to soil containing resting spores that had been collected in the field and stored at 4°C for varying lengths of time. No differences in infection occurred among larvae exposed to fall-collected soil samples stored at 4oC over the winter, versus soil samples collected from the same location the following spring. Springcollected resting spores stored at 4°C did not go into secondary dormancy. At the time that cold storage of soil containing resting spores began in spring, infection among exposed larvae was initiated within a few days after bringing the soil to 15°C. This same pattern was also found for spring-collected resting spore-bearing soil that was assayed after cold storage for 2-7 months. However, after 31-32 months in cold storage, infections started 14-18 days after soil was brought to 15°C, indicating a delay in resting spore activity after prolonged cold storage.     

Temperature-dependent germination traits in oilseed rape associated with 5'-anchored simple sequence repeat PCR polymorphisms

An experiment was conducted to test the hypothesis that phenotypes differing in germination rate and the presence or absence of secondary dormancy at low temperature were not genetically different. Seed of oilseed rape was germinated at 4, 10 and 19 degrees C, where selections were made in the percentile ranges 1-10 (early), 45-55 (intermediate) and 91-100 (late). Secondary dormancy occurred only in the late selections at the two lower temperatures. Thermal weighting of curves of cumulative germination on time gave circumstantial evidence that early percentiles were similar at all three temperatures and that seeds with secondary dormancy came largely from later percentiles above the 50th. To test for genetic differentiation between phenotypes, 5'-anchored simple sequence repeat primers were used to generate DNA marker profiles of seedlings raised from seed from each category. Principal coordinate analysis, and more detailed comparisons using the most discriminating markers, confirmed that the early germinators at the three temperatures were not associated with different banding profiles, but seeds entering secondary dormancy, particularly at 10 degrees C, were genetically distinct from germinators at the same temperature. Secondary dormant seeds at low temperature appear to originate mainly from the late germinating seed at higher temperature. Effects of temperature history and the requirement for alternating temperatures to break secondary dormancy were quantified. The results confirm the existence of genetically discrete sub-populations differing in ecologically significant traits.     

Germination Ecophysiology of the Mesic Deciduous Forest Herb Polemonium reptans var. reptans (Polemoniaceae)

Abstract Seeds of Polemonium reptans var. reptans , a perennial herb of mesic deciduous forests in eastern North America, mature in late May-early June, and a high percentage of them are dormant. Seeds afterripened (came out of dormancy) during summer when kept in a nylon bag under leaves in a nonheated greenhouse or on wet soil in a 30/15°C incubator. The optimum temperature for germination of nondormant seeds was a simulated October (20/10°C) regime. In germination phenology studies in the nonheated greenhouse, 20–30% of the seeds that eventually germinated did so in October, and the remainder germinated the following February and March. Since low (5°C) winter temperatures promote some afterripening (ca. 50%) and do not cause nondormant seeds to re-enter dormancy, seeds that fail to germinate in autumn may germinate in spring. Thus, the taxon has very little potential to form a persistent seed bank. The large spatulate embryos and ability of seeds to afterripen at high temperatures means that seeds of P. reptans var. reptans have nondeep physiological dormancy, unlike many herbaceous woodland species, which have morphophysiological dormancy.     

Ethylene as a possible cue for seed germination of Schoenoplectus hallii (Cyperaceae), a rare summer annual of occasionally flooded sites

The purpose of our research was to determine why seeds of Schoenoplectus hallii germinate only in some wet years. Seeds mature in autumn, at which time they are dormant. Seeds come out of dormancy during winter, if buried in nonflooded, moist soil, but they remain dormant if buried in flooded soil. Nondormant seeds require flooding, light, and exposure to ethylene to germinate. One piece of apple in water (1/12 of an apple in 125 mL of water in a glass jar for a depth of 5 cm) or a 1-μmol/L solution of ethephon elicited very similar (high) germination percentages and vigor of seedlings. Apple, which was shown to produce ethylene in the air space of the jar, was used in a series of experiments to better understand germination. Seeds germinated to 72% if apple was removed from the water after 1 d of incubation, and they germinated to 97% if seeds were washed and placed in fresh water after 3 d of exposure to apple. No seeds germinated in control with no apple. Seeds incubated in apple leachate for 5 d and then transferred to filter paper moistened with distilled water germinated to 90%. Minimum depth of flooding in apple leachate (no soil in jars) for optimum germination was ≥3 cm. Buried seeds of S. hallii exhibited an annual conditional dormancy/nondormancy cycle. Regardless of the month in which seeds were exhumed, they germinated to 59-100% in light in water with apple at daily alternating temperature regimes of 25°/15°, 30°/15°, and 35°/20°C, but germination at 20°/10°C (and to some extent at 15°/6°C) tended to peak in autumn to spring. Thus, seeds can germinate throughout the summer if flooded (ethylene production) and exposed to light. An ethylene cue for germination serves as a "flood-detecting" mechanism and may serve as an indirect signal that water is available for completion of the life cycle and competing species are absent.     

Endosperm dormancy breakage in olive seeds

Seeds of Olea europaea L. ssp. oleaster Hoffm. and Link freed from the sclerous endoearp and incubated in water at 15 or 25°C in darkness or in 12:12 h white light:dark conditions, did not germinate, due to dormancy imposed by the endosperm. Seeds also did not germinate when incubated in abscisic acid, gibberellic acid, kinetin or zeatin in darkness and at cither 15 or 25°C. SAN 9789 |4-chloro-5-(methylamine)-2-(a,a,a-trifluoro-m-tolyl)-3-(2H)-pyridazmone] did not promote germination at 15°C but it did to a 75% level at 25°C. This promoting effect of SAN was counteracted by abscisic acid. Cultures of naked embryos grew equally well in the presence or absence of SAN 9789. 6-Benzylaminopurine promoted whole seed germination to a 15% level.     

Seed germination and seedling growth of the Mexican sunflower Tithonia diversifolia (Compositae) in Nigeria, Africa

We studied seed germination and seedling growth of the Mexican sunflower Tithonia diversifolia in Nigeria. This involved the usage of some dormancy-releasing methods and the effect of some concentrations of three herbicide formulations on the young seedlings. Initial germination tests on fresh and stored seeds revealed a low percentage germination of less than 30%. The seeds of the weed exhibit dormancy. Subjecting the seeds to wet heat at 80 and 100 degrees C and light treatment terminated dormancy both in the fresh and stored seeds. Light greatly enhanced the germination percentage of seeds by about 70%. There was gradual increase in germination percentage with increase in storage period in dormancy-released seeds. The mean LAR (Leaf Area Ratio), NAR (Net Assimilation Rate) and RGR (Relative Growth Rate) are comparatively high in young seedlings. Concentrations of 0.5-2.0% of Gramoxone, Primextra and Galex are toxic to 1 month old seedlings. For eradication, the seedlings should be attacked at one month stage.     

画眉草种子萌发对策及生态适应性

研究了画眉草种子在不同贮藏条件以及光照、温度和降雨等环境因素下的萌发对策.结果表明,画眉草新种子具有较强的内在休眠;4个月的干藏和冷藏处理对解除种子休眠作用不明显,但较长时间的贮藏（干藏1年）则能促进种子成熟.画眉草种子在光照和黑暗条件下都能萌发,但较强的光照更有利于种子萌发.种子萌发适宜温度是28 ℃,温度升高和降低都会导致画眉草种子萌发率下降;变温条件下（16～28 ℃）种子萌发率高于恒温28 ℃条件,但两个处理间的萌发率没有显著差异.种子萌发降雨阈值是10 mm,种子萌发率和萌发持续时间均随降雨量的增加而增加.画眉草种子具有迅速萌发和推迟萌发时间超过1年以上两种萌发对策.根据种子形态特征和萌发策略,推断画眉草具有持久土壤种子库.     

狼毒种子萌发特性与种群更新机制的研究

研究了采集于植株上的和收集于土壤种子库的狼毒(Stellera chamaejasme)种子在不同温度、光照和5种预处理(即破裂种皮、去除种皮、98％H2SO4浸种5min、0．2％KNO3浸种24h、10℃低温保存1周)条件下的萌发力。结果表明,狼毒种子萌发率较低,25℃恒温、黑暗条件下萌发率为13％,较适宜的萌发温度为30℃恒温或10～30℃变温,破裂种皮和去除种皮萌发率显著提高,25℃恒温、光暗交替条件下萌发率分别为49％和47％,浓硫酸浸种5min处理萌发率可达到32％,KON3浸种和10℃低温保存两个处理对促进狼毒种子萌发效果不明显,狼毒种子萌发对光照条件不敏感,种子硬实性是导致狼毒种子萌发率较低的主要原因,取自土壤种子库内的狼毒种子萌发率高于当年采集的种子,在自然条件下,并非每年都有狼毒种子萌发长成幼苗,种群更新时机是随机的或周期性的。