青钱柳天然群体种子性状表型多样性

以青钱柳分布区内的9个天然群体种子为试材,对种子千粒重、体积、直径、厚度和径厚比5个表型性状进行了系统的比较分析,采用方差分析、相关分析及聚类分析等方法对群体间和群体内的表型多样性进行探讨.结果表明: 青钱柳种子千粒重、体积、直径及厚度在群体间和群体内均达到显著或极显著差异,而种子径厚比仅在群体内存在极显著差异,说明青钱柳种子性状在2个层次上都具有丰富的多样性.各性状的平均表型分化系数（V）为20.54%,即群体间的变异远低于群体内的变异（79.46%）.种子性状与地理因子相关程度存在差别,且受年均气温的影响最大.利用群体间欧氏距离进行系统聚类分析,青钱柳群体可以划分为三类.     

祁连山青海云杉天然群体的种实性状表型多样性

 以系统揭示其表型变异程度和变异规律为目的，对祁连山青海云杉(Picea crassifolia )天然分布区的10个群体的8个种实性状进行了比较分析。采用方差分析、多重比较，相关分析、聚类分析等多种分析方法，对群体间和群体内的表型多样性进行了讨论。方差分析结果表明，各种实性状在群体间都存在极显著差异，除球果干质量和球果长/球果径外，其余性状在群体内都存在着极显著的差异；表型分化系数即群体间变异为27.18%，小于群体内的变异(72.82%)；球果长、球果径、球果干质量、球果形状指数、种子长、种子宽、千粒重和种子形状指数的变异系数分别为：10.08%、5.80%、19.29%、9.66%、8.38%、15.34%、6.52%和13.94%；8个种实性状间多数呈极显著或显著的正相关，球果干质量、种子长、千粒重、球果长和球果径为青海云杉易测定和重要的种实性状；种实性状呈现出以经度变异为主的梯度规律性；通过表型性状的聚类分析可以将青海云杉10个群体划分为4类。     

皂荚南方天然群体种实表型多样性

以系统揭示表型变异程度和变异规律为目的,对皂荚(Gleditsia sinensis)南方分布区的10个天然群体的11个种实性状进行了比较分析.采用方差分析、多重比较、相关分析等多种分析方法,对群体间和群体内的表型多样性以及与地理、环境因子的相关性进行了讨论.方差分析结果表明;皂荚果实、种子等性状在群体间和群体内存在丰富的变异,1 1个性状在群体间、群体内均达显著差异;荚果性状在群体间和群体内的变异均大于种子性状,11个性状的平均表型分化系数为20.42％,群体内的变异(32.28％)大于群体间的变异(7.19％),群体内的变异是皂荚的主要变异来源;皂荚各性状平均变异系数为11.20％,变异幅度为4.55％-18.38％.群体间荚果的变异(14.75％)高于群体间种子变异(6.95％),表明种子变异稳定性高.荚果和种子各性状之间多呈极显著或显著正相关,表现为荚果越大,则种子越大,种子的千粒重也越大;荚果表现为同地理经度的南北变异,种子则表现为同地理纬度的东西变异.研究结果为进一步开展皂荚遗传育种、保护生物学研究和皂荚种质资源利用奠定了基础.     

我国格木的地理分布与种实表型变异

在调查格木（Erythrophleum fordii）主要天然分布区及资源现状的基础上,研究了荚果和种子的11个表型性状在8个格木天然群体内和群体间的变异规律,探讨了种实表型变异与地理、环境因子的相关性。结果显示：格木天然林主要分布在广西、广东和福建3省区北回归线附近低海拔地区,大部分呈散生状态或小群体：格木荚果和种子的长度、宽度、形态指数以及每个荚果内种子数、种子厚度和千粒重在群体间和群体内单株间均存在显著差异：荚果性状在群体间和群体内的变异均大于种子性状：每个荚果内种子数与荚果的长度、形态指数以及种子的长度、大小呈显著正相关,种子长度和宽度与荚果大小、种子千粒重与荚果宽度均呈显著正相关：荚果形态指数与经度呈显著负相关,种子千粒重与纬度、种子宽度与海拔和年降雨量、种子形态指数与年均气温、种子大小与年降雨量均呈显著正相关。通过聚类分析可将8个格木群体分为3类：GX03单独为1类,GX01与GX02聚为1类,其余5个群体聚为1类。研究结果为进一步开展格木保护生物学和遗传育种研究奠定了基础。     

我国格木的地理分布与种实表型变异

在调查格木(Erythrophleum fordii)主要天然分布区及资源现状的基础上, 研究了荚果和种子的11个表型性状在8个格木天然群体内和群体间的变异规律, 探讨了种实表型变异与地理、环境因子的相关性。结果显示: 格木天然林主要分布在广西、广东和福建3省区北回归线附近低海拔地区, 大部分呈散生状态或小群体; 格木荚果和种子的长度、宽度、形态指数以及每个荚果内种子数、种子厚度和千粒重在群体间和群体内单株间均存在显著差异; 荚果性状在群体间和群体内的变异均大于种子性状; 每个荚果内种子数与荚果的长度、形态指数以及种子的长度、大小呈显著正相关, 种子长度和宽度与荚果大小、种子千粒重与荚果宽度均呈显著正相关; 荚果形态指数与经度呈显著负相关, 种子千粒重与纬度、种子宽度与海拔和年降雨量、种子形态指数与年均气温、种子大小与年降雨量均呈显著正相关。通过聚类分析可将8个格木群体分为3类: GX03单独为1类, GX01与GX02聚为1类, 其余5个群体聚为1类。研究结果为进一步开展格木保护生物学和遗传育种研究奠定了基础。     

长白落叶松结实与发芽特性

以落叶松种子园中21个长白落叶松无性系亲本为试验材料,对其结实和发芽性状进行研究,分析其遗传变异状况,以期筛选结实及发芽均表现优良的无性系。方差分析结果表明各无性系结实和发芽性状间存在极显著差异,其中无性系L52和L67平均发芽特性表现较好。各性状表型变异系数变化范围为13.34%～69.47%,遗传力变化范围为0.7757～0.9463,高变异系数、高遗传力有利于优良无性系评价选择。相关分析结果表明各性状间相关系数变化范围为0.054～0.889,其中种子发芽率、发芽势、发芽指数与千粒重、种子长度、种子宽度存在显著或极显著正相关,表明种子发芽特性与种子表型间存在较为密切的联系。最终以发芽率、发芽势和发芽指数为指标进行聚类分析,将各无性系种子聚为两类,无性系L17、L40、L49、L52、L55、L67、L71、L88和L99种子发芽性状较优良,可作为高发芽率优良亲本进行利用,此研究可为长白落叶松种子园亲本选择提供依据。     

梭梭不同种源间种子性状和幼苗生长性状与地理和气候因子的关系

对6个种源区梭梭[Haloxylon ammodendron(C.A.Mey.)Bunge]的种子性状和幼苗生长性状进行比较,并对这些性状与地理气候因子的相关性进行了分析,通过聚类分析方法对不同种源进行了评价.结果显示,不同种源间梭梭种子性状和幼苗生长性状存在显著差异,种子的果翅长度、种子千粒重、单株种子质量和种子发芽率的变化范围分别为5.13～7.14 mm、2.21～3.75 g、2.49～53.17 g和24.45%～75.00%,幼苗株高、新生枝长度、幼苗地径和幼苗成活率的变化范围分别为16.67～56.67 cm、14.33～29.34 cm、4.04～8.06 mm和42.56%～84.45%.不同种源梭梭的种子及幼苗生长性状与地理分布有关;单株种子质量、种子发芽率、幼苗株高和幼苗成活率与经度极显著正相关,果翅长度、种子千粒重和幼苗株高与纬度极显著负相关,海拔仪与果翅长度有显著相关关系;单株种子质量、种子发芽率和幼苗成活率的直接影响因子为经度,果翅长度、种子千粒重和新生枝长度的直接影响因子为纬度.气候因子与种子性状紧密相关,而与幼苗生长性状的相关性较差,仅幼苗成活率与1月气温和相对湿度存在极显著相关性;1月气温对果翅长度、单株种子质量、种子发芽率、幼苗株高和新牛枝长度的直接作用最大;年降雨量对地径的直接作用最大,相对湿度对幼苗成活率的直接作用最强.通过聚类分析将6个梭梭种源分为3类,其中内蒙古磴口种源为优良梭梭种源,新疆乌苏种源为较差种源.     

花楸树天然群体种实多样性研究

以花楸树分布区(山东省、山西省、河北省、辽宁省)的8个天然群体为试材,对其果实、种子特性等9个性状进行比较分析,讨论群体间和群体内的表型多样性.结果表明,花楸树果实、种子特性等性状在群体间和群体内均存在极其丰富的变异,9个性状在群体间、群体内均达显著或极显著差异.9个性状的平均表型分化系数为45.76%,群体内的变异(40.58%)大于群体间的变异(36.81%),说明群体内的变异是花楸树的主要变异来源.花楸树果实、种子性状与地理生态因子的相关分析表明,纬度、海拔、年均温、年降雨量与其性状呈显著相关.     

贵州省野生皂荚种实表型性状多样性分析

为深入了解贵州省野生皂荚(Gleditsia sinensis)荚果表型性状的遗传多样性及其变异类型,为皂荚的遗传改良、种质鉴定、亲本选择以及品种培育奠定理论基础。该研究以贵州省7个野生皂荚群体70个个体为研究对象,采用方差分析、主成分分析、相关性分析及多性状综合评价等方法对皂荚群体的10个种实表型性状进行系统分析和综合评价。结果显示：(1)所测皂荚的表型性状差异在群体内均达到极显著水平(P＜0.01);在群体间,除每荚粒数、种子宽、种子长宽积以及种子长宽比之外,其余表型性状的差异均达极显著水平(P＜0.01)。(2)7个居群野生皂荚各性状平均变异系数为21.16%,其中凯里市(P4)居群的变异系数最高(24.44%);居群间荚果的变异(29.22%)高于种子的变异(11.04%),且变异主要来自于群体内。(3)相关分析显示,皂荚种实各性状之间存在不同程度的关联性;主成分分析显示,前4个主成分(皂荚种子大小、单个荚果出籽数量、种子形态指数因子、与荚果长和种子厚相关的因子)的累积贡献率达69.783%,可基本反映皂荚表型性状的大部分信息;以10个种实性状对皂荚野生群体进行综合评价发现,来自于惠水县(P7)群体的皂荚种实性状综合评价最高。研究表明,贵州省野生皂荚在群体间及群体内具有丰富的表型变异,且群体内的变异大于群体间的变异,变异主要来自于群体内。     

卫星搭载鸡冠花种子SP2代的生长、发育与性状变异研究

对卫星搭载处理的鸡冠花SP2代种子萌发、植株生长、开花以及主要性状在群体中的变异进行了观察.与对照比较,SP2种子发芽势提高,发芽率有所下降,萌发延迟.群体茎粗与对照相比显著增加;选择系在株幅、茎粗间出现了较大差异.在SP2株系间开花时间和花期出现了明显分离,株系群体中有花期明显提前和延迟的单株出现.20个株系中有16个株系的单株种子量比对照显著减少.在SP2株系中株高、株幅呈非正态分布,茎粗和花期呈偏正态分布.在处理的株系群体中有植株显著高大、多分枝、叶色、叶型、冠型、冠色及花期等显著性状变异出现,产生性状变异的单株频率为0.07％-1.26％,表明空间诱变所产生的变异性状开始在SP2代出现.     

荒漠植物红砂抗旱性与其电学参数关系的研究

为了研究电学参数与红砂(Reaumuria soongorica)抗旱性的关系,以4个地理种源的荒漠植物红砂2年生苗木为材料,测定其茎在不同干旱胁迫处理下的高频电阻(r)、低频电阻(rl)、胞外电阻率(re)、胞内电阻率(ri)、电导(G)和电纳(B)等电学参数以及膜透性(RPP)和渗透调节物质脯氨酸(Pro)含量的变化,分析电学参数与膜透性和脯氨酸含量间的相关性。结果显示,随着干旱胁迫的加剧,4个地理种源红砂茎的膜透性和脯氨酸含量均呈逐渐升高或先升高后降低趋势,不同种源间存在显著差异(P0.05)。红砂茎膜透性的大小在4个种源间表现为:兰州张掖酒泉武威,脯氨酸含量由高到低依次为武威酒泉张掖兰州。4个地理种源红砂茎的高频电阻呈逐渐下降趋势,胞外电阻率、胞内电阻率、电导呈先升高后降低的趋势,而低频电阻则与它们相反,电纳的变化则较为复杂。6个电阻参数在不同种源材料间和不同处理间差异均显著(P0.05)。相关性和通径分析结果表明,胞外电阻率、胞内电阻率、高频电阻和电纳与膜透性的相关性较为明显;胞外电阻率、胞内电阻率、高频电阻和电导与脯氨酸含量的相关性较为显著,其中胞内电阻率对膜透性和脯氨酸含量的影响最大,通径系数绝对值分别高达0.938和0.897。说明电学参数ri可以作为表征红砂抗旱特性的参数,也表明电学方法将是荒漠植物逆境胁迫研究的一种有效方法。     

The role of domestication and maternal effects on seed traits of crop–wild sunflower hybrids (Helianthus annuus)

Hybridisation between crops and their wild relatives may promote the evolution of weeds. Seed germination and dormancy are the earliest life‐history traits and are highly influenced by the maternal parent. However, the ecological role of the maternal effect on seed traits in the evolution of crop–wild hybrids has received little attention. In this study, we test the relative importance of maternal and hybridisation effects on seed traits of the first generation of crop–wild sunflower hybrids (Helianthus annuus). Seed germination was tested in two wild populations with contrasting dormancy, two cultivated materials and their reciprocal crosses at four different times after harvest and three different temperatures. Seed germination at each of the four times, after ripening response and secondary dormancy were recorded along with four morphological traits. Additionally, the pericarp anatomy was analysed with light and scanning electron microscopy. We observed strong maternal effects on all seed traits. Seed germination, morphology and pericarp anatomy differed largely between the crop and wild seeds and these traits in the crop–wild hybrids resembled their female parent. Slight but significant hybridisation effects were observed in germination, mainly in seeds produced on wild plants. Crop hybridisation changed seed germination, the after ripening response and secondary dormancy in the crop direction. Morphological and anatomical traits associated with domestication strongly correlated with the observed differences in seed germination and dormancy in crop–wild sunflower hybrids. The large maternal effects along with the evolutionary divergence in seed traits were responsible for the large phenotypic differences observed in crop–wild hybrids with the same genetic composition. Wild‐like seed traits of hybrids suggest that there are no barriers to crop gene introgression at the seed level whereas crop‐like seed traits could be strongly selected against, conditioning the selection of traits expressed later in the life cycle and in the next generations.     

霸王果翅及其浸提液对种子萌发的影响

在室内控制条件下,研究了霸王果翅对其种子萌发及果翅浸提液对霸王、红砂与无芒隐子草3种荒漠植物种子萌发的影响.结果表明:(1)果翅可完全抑制霸王种子的萌发.具有完整果翅的霸王种子萌发率为0;剥去果翅后霸王种子萌发率最高达91%;果翅刺破后其发芽率为4O%;而将种子与剥离后的果翅一起培养,其发芽率为88%.(2)果翅浸提液在低浓度条件下(0.025 g/Ml)对3种供试种子的萌发率均无显著影响.但高浓度浸提液(>0.025 g/Ml)则均显著降低种子萌发率;不同浓度浸提液均显著降低3种种子的萌发速率,对其胚根生长亦存在显著抑制作用;但对胚芽生长的影响则表现为低浓度(0.025 g/Ml)具促进作用,而高浓度具抑制作用.研究表明,霸王果翅可引起种子休眠,其浸提液中的萌发抑制物是引起种子休眠的主要方式.     

Altitudinal variations in germination and growth responses ofReynoutria japonica populations on Mt Fuji to a controlled thermal environment

The authors examined altitudinal variations in the thermal responses of seed germination and seedling growth inReynoutria japonica (=Polygonum cuspidatum) under controlled environmental conditions. Seed populations were collected from different altitudes on Mt Fuji in Japan. The mean seed weight of the upland populations (above 1500 m) was significantly (1.5-fold) heavier than that of the lowland populations (below 1400 m). Under the lowest temperature regime of 15/10°C (day/night) the upland populations showed a significantly higher percentage and speed of germination than the lowland populations; this was not significant under higher temperature regimes. These results indicate that the germination traits of the upland populations on Mt Fuji are favorable for colonization in their cold habitats (low temperature and short growing season). Growth and shoot development were compared between the seedlings grown from seeds collected at altitudes of 700 and 2420 m. The upland seedlings showed a significantly larger biomass and leaf area than the lowland seedlings at 15°C, but there was no difference at 25°C. The difference in biomass at 15°C was attributed to the difference in seed weight. The upland seedlings produced a significantly larger number of branches with smaller and more numerous leaves at both 15°C and 25°C. these developmental traits of the upland seedlings were considered to represent the adaptation of the life form to upland environments. It was concluded that theR. japonica populations along an altitudinal gradient on Mt Fuji can be classified into two ecotypes, whose distribution border lies at an altitude of about 1400–1500m. In this study, the seed weight and germination traits of twoR. japonica seed populations collected in Chiba Prefecture were briefly compared with those of the lowland populations on Mt Fuji.     

Rainfall seasonality predicts the germination behavior of a tropical dry‐forest vine

Seed dormancy is considered to be an adaptive strategy in seasonal and/or unpredictable environments because it prevents germination during climatically favorable periods that are too short for seedling establishment. Tropical dry forests are seasonal environments where seed dormancy may play an important role in plant resilience and resistance to changing precipitation patterns. We studied the germination behavior of seeds from six populations of the Neotropical vine Dalechampia scandens (Euphorbiaceae) originating from environments of contrasting rainfall seasonality. Seeds produced by second greenhouse‐generation plants were measured and exposed to a favorable wet environment at different time intervals after capsule dehiscence and seed dispersal. We recorded the success and the timing of germination. All populations produced at least some dormant seeds, but seeds of populations originating from more seasonal environments required longer periods of after‐ripening before germinating. Within populations, larger seeds tended to require longer after‐ripening periods than did smaller seeds. These results indicate among‐population genetic differences in germination behavior and suggest that these populations are adapted to local environmental conditions. They also suggest that seed size may influence germination timing within populations. Ongoing changes in seasonality patterns in tropical dry forests may impose strong selection on these traits.     

Seed weight and germination behavior of the submerged plant Potamogeton pectinatus in the arid zone of northwest China

Variation in seed weight is common within and among plant species, but few studies have attempted to document the pattern of seed weight and germination attributes for aquatic macrophytes at a large scale. This study examined within‐species variation in seed weight and germination attributes and the effects of environmental factors on seed traits of the submerged plant Potamogeton pectinatus in the arid zone of northwest China. Our results showed that the average seed weight was 0.24 g per 100 seeds with a coefficient of variation (CV) of 28.4% among the eight P. pectinatus populations. The total germination fraction of seeds of P. pectinatus was relatively poor, less than 35% in seven P. pectinatus populations, and the lowest germination percentage found was only 2%. There were significant differences in seed weight, time to onset of germination, and total germination fraction among the eight different populations. Hierarchical partitioning analysis showed a strongly positive correlation between seed weight and water temperature and pH. Seed weight and the maternal environmental factors significantly affected both time to initiation of germination and total germination fraction. Our results suggest that (1) seed weight variation in P. pectinatus primarily is the result of temperature variation during fruit development; (2) relatively poor germination fraction suggests that seeds are relatively unimportant in the short‐term survival of populations and that it may be another adaptive trait allowing plants to take place in the right place and at the right time, especially in harsh environment; and (3) variation in seed germination traits should be determined by local environmental and intrinsic factors that interact in a complex fashion.     

Climatic control of germination in the genus Silene L

Background: Seed germination strategies depend on a number of factors such as climatic variables, habitat, life cycle, phylogenetic affiliation and morphological seed traits.

Aims: We present a novel evaluation of the ecological correlates of germination strategies focussing on plant populations drawn from a single genus and considering a number of relevant explanatory variables.

Methods: Temperature and light-controlled germination experiments were carried out on 21 seed accessions belonging to 13 closely related species of the genus Silene L. Accessions were selected to tightly control the phylogenetic effect and give broad ecological and geographic coverage of the genus in Europe, with three North American and Macaronesian outgroups from climatically extreme environments. We used principal component analysis and correlation analyses to identify the correlation structure of germination traits and include multiple explanatory variables.

Results: Three germination strategies were shown to be related to climatic control. (1) Seeds from arid regions with hot, dry summers germinated optimally at cool temperatures associated with the rainfall period under field conditions, whereas (2) the benefit of cold stratification was more marked in provenances characterised by cold, dry winters, and (3) seeds from mild climates preferred warm temperatures for germination. Moreover, (4) biennial populations of disturbed habitats showed synchronised and rapid seed germination over a wide thermal window. In agreement with previous findings, (5) habitat-related syndromes were observed only for wetland populations. Correlations with seed mass were significant when related to summer precipitation, but weak or absent in relation to germination traits, indicating that, though influenced by the local climate, seed mass is a poor predictor of germination strategies.

Conclusions: These results suggest that whilst habitat and life cycle might shape germination patterns to a certain extent, long-term climatic differences play a substantial role in selecting specific germination traits and strategies.     

不同居群准噶尔无叶豆果实和种子特性及种子萌发差异

研究准噶尔无叶豆(Eremosparton songoricum) 6个居群间果实和种子特性及种子萌发差异, 以揭示异质生境下准噶尔无叶豆果实和种子的生态适应机制。结果显示: 居群间准噶尔无叶豆的植株距离(F = 2.34, p = 0.03)和植株冠幅(F = 8.49, p < 0.01)存在显著差异, 沙漠北缘E、F居群和沙漠腹地C居群(受人类干扰剧烈)的植株距离和植株冠幅高于沙漠腹地A、B、D居群; 居群间准噶尔无叶豆果实和种子的长度、宽度、厚度、重量存在显著差异, 居群E、F和C的大部分参数显著高于其他沙漠腹地居群; 居群间果实多子性(F = 6.96, p < 0.01)也存在显著差异, 居群C的果实多子性最高((32.50 ± 4.79)%); 萌发结果表明, 居群间新鲜的成熟种子萌发不存在显著差异, 且萌发率都低于15%; 所有居群的大部分种子都存在物理性休眠现象, 人为划破种皮能显著提高种子萌发率, 但在低温(15/5 ℃)条件下, 所有居群的种子萌发率都较低, 说明低温抑制了种子萌发; 经人为划破种皮解除物理休眠后, 种子的休眠没有完全释放, 居群C、E和F (大种子居群)的种子萌发率显著高于居群A、B和D (小种子居群) (F = 30.77, p < 0.01), 说明准噶尔无叶豆种子不仅存在物理性休眠现象, 也可能存在生理休眠现象。不同程度的种子复合休眠可能是准噶尔无叶豆不同居群适应古尔班通古特沙漠的重要生存策略。     

黑果枸杞种子萌发及幼苗生长对盐胁迫的响应

研究不同浓度(0、1、2、3、6、9、14、18g.L-1)的盐溶液(NaCl、MgSO4、盐渍土壤)对河西走廊中部荒漠边缘的黑果枸杞种子吸胀、萌发和幼苗生长的影响,并观察胁迫解除后种子的反应。结果表明:黑果枸杞种子吸胀速率随NaCl、MgSO4和土壤溶液浓度的增大呈先升后降的趋势,吸水速度随胁迫时间的延长而减慢;种子萌发率随3种盐浓度的增大而降低,盐胁迫解除后种子仍具有较高的萌发率;发芽指数、活力指数、根长、下胚轴随3种盐浓度的增大而降低或先升后降,根轴比随盐胁迫的增强先升后降;随3种盐浓度的增大,种苗损害率增大,3种盐的胁迫效应依次NaCl>MgSO4>盐渍土壤溶液。黑果枸杞种子萌发和幼苗生长对NaCl胁迫较为敏感,其耐受的临界阈值是6g.L-1;种子萌发能耐受较高浓度的MgSO4的胁迫,幼苗生长对MgSO4胁迫较敏感,其耐受的临界阈值是9g.L-1;种子萌发和幼苗生长对生境盐渍土壤具有较强的耐受能力和适应性。     

Seed dormancy and longevity in <Emphasis Type="Italic">Stipa tenacissima</Emphasis> L. (Poaceae)

In the present paper we studied the life history traits related to seed germination of Stipa tenacissima, a key species in semiarid environments of western Mediterranean areas. S. tenacissima is a perennial tussock grass, which has traditionally been considered to expand mainly by vegetative propagation with little or no sexual reproduction. We analysed seed longevity as well as the type of seed dormancy and the role of the seed covers from seeds collected from different populations in SE Spain. We also studied the variation in seed germinability among populations, individuals, and years and the ability of seeds of S. tenacissima to form soil seed banks. There was significant variation in seed germination among individuals, populations and years. Lemma and palea were the main factor controlling these differences since their removal promoted higher and faster germination and eliminated the differences in germination parameters among populations. However, the control of dormancy by lemma and palea was independent of their weight, suggesting that their chemical nature plays a more important role than does size in controlling seed germination. Mechanical scarification treatments (via abrasion with sand) did not affect seed germination. The decay in seed germinability two years after seed collection and the low density of viable seeds in soils one year after seed dispersal indicated that S. tenacissima forms transient soil seed banks.