温度和光照对3种雀麦属(Bromus)植物种子萌发的影响

旱雀麦(Bromus tectorum)原产于欧亚大陆,18世纪传入北美,并成为该地区的入侵植物。然而,同为雀麦属的扁穗雀麦(Bromus catharticus)和无芒雀麦(Bromus inermis)并不具有旱雀麦的入侵性。本研究设置高温、低温和黑暗等处理,探讨温度和光照对3种植物种子萌发的影响,旨在从种子萌发的角度揭示旱雀麦的入侵性。结果表明:温度和光照对旱雀麦和扁穗雀麦种子的发芽率均无明显影响(p>0.05);高温和黑暗处理显著提高了无芒雀麦种子的发芽率(p<0.05),对旱雀麦、扁穗雀麦和无芒雀麦种子的发芽势、发芽指数、日均发芽率、发芽系数、发芽峰值和发芽值有一定的促进作用,而低温处理则表现出相反的效应;高温和黑暗处理对3种植物种子的平均发芽天数和萌发持续时间有一定降低的作用,而低温处理则表现出相反的效应。同一处理下旱雀麦种子萌发各项指标均优于另两种植物,这可能是旱雀麦具有较强入侵性的重要原因。     

原生地和入侵地旱雀麦(Bromus tectorum)幼苗生理特性比较

以来自中国准噶尔盆地(原生地)和美国大盆地(入侵地)的一年生禾本科植物旱雀麦(Bromus tectorum)为研究对象,对比分析了不同来源地之间旱雀麦幼苗生理特性的差异.结果表明:(1)来自大盆地旱雀麦的主要光合作用指标均极显著地高于准噶尔盆地旱雀麦,具体表现为:净光合速率、气孔导度、蒸腾速率、瞬时水分利用效率及最大净光合速率均存在显著性差异(p＜0.01),而胞间CO2浓度及其他光合作用参数的差异不显著(p＞0.05);(2)叶绿素荧光参数方面,调节性能量耗散量子产量、非调节性能量耗散量子产量以及非光化学淬灭系数表现出显著差异(p＜0.05),其他荧光参数的差异不显著(p＞0.05);(3)来自大盆地旱雀麦幼苗叶片叶绿素a、叶绿素b、叶绿素a+b的含量以及叶片含氮量均高于准噶尔盆地旱雀麦,但差异并不显著(p＞0.05).总体来说,来自大盆地旱雀麦幼苗在生理特性方面要比准噶尔盆地旱雀麦具有一定的优势.     

荒漠植物种子萌发研究进展

 对种子自身结构,水分、温度、光照、沙埋深度等对荒漠植物种子萌发的影响进行了综述。硬实种子的不透水性、不透气性以及物理障碍是影响种子萌发的重要因素,通过热水浸种、擦破种皮或果皮、浓硫酸浸泡、低温或辐射处理可以破除硬实的影响。有些荒漠植物果皮或种皮外包有粘液层,这种结构对种子的萌发及幼苗生长有促进作用;部分植物的种胚覆盖物含有生长抑制物质而抑制种子萌发;胚休眠与后熟是影响胚萌发的重要生理因素。雨量大小、分布,降雨次数及土壤湿度是决定荒漠植物种子萌发的重要生态因子;温度影响种子的萌发,变温促进萌发;部分荒漠植物种子的萌发需要光照,有些要在暗中萌发,有些则对光无特异的需求;沙埋深度可调节光照、土壤湿度和土壤温度,从而调节种子萌发。应重视荒漠植物种子对严酷环境适应的研究,从分子水平上阐述其对严酷生境的适应机制。     

胡杨(Populus euphraticu)与灰胡杨(Populus pruinosa)种子萌发对不同盐类胁迫的响应

将塔里木荒漠优势种——胡杨(Populus euphraticu)和灰胡杨(Populus pruinosa)的种子置于8种浓度的NaCl(单盐)和土盐(复合盐)溶液中进行发芽实验,探讨两树种种子对不同盐类的耐受限度和适应萌发生境,采用隶属函数法综合评价其耐盐性.结果表明:两树种种子发芽率、相对发芽率、发芽势、发芽指数和子叶展平率均随NaCl浓度的增加而下降,相对盐害率升高.二者种子相对发芽率在浓度＜0.4％的NaCl溶液中均超过75％,NaCl胁迫下2种种子发芽率无显著差异(p＞0.05).单盐处理下胡杨种子的各项发芽指标均优于灰胡杨,表明胡杨的耐盐(NaCl)能力强于灰胡杨.低浓度土盐溶液对二者种子萌发均具有促进作用,发芽率和发芽指数明显升高,而高浓度土盐溶液则抑制种子萌发.二者种子相对发芽率在浓度＜0.8％的土盐溶液中均超过80％,且1.6％盐浓度下仍高于20％,此值远高于NaCl胁迫.土盐处理下两树种种子发芽率差异达极显著水平(p＜0.01).土盐处理下灰胡杨种子的各项发芽指标均优于胡杨,表明灰胡杨对土盐具有较强的适应性和耐盐能力.NaCl胁迫对二者种子萌发的抑制作用大于土盐.胡杨、灰胡杨均具有较强的耐盐性,但早期低盐条件是两树种幼苗建立的关键.     

准噶尔无叶豆地理种群种子萌发特性

准噶尔无叶豆种子具有明显的地理种群大小变异的现象。对大、小种子在3种光照(持续光照,12/12小时光照/黑暗,全黑暗)、5个温度梯度(10℃,15℃,20℃,25℃,30℃)条件下的最适萌发条件进行研究,结果表明:大、小种子萌发的适宜光照条件均为12/12小时光照/黑暗,在持续黑暗与持续光照条件下的萌发率无显著差异;最适温度范围是20~25℃,大种子在20℃、25℃下的萌发率(>85%),萌发指数均显著高于相同温度条件下小种子的萌发率(<35%)和萌发指数。大种子存在种皮硬实所导致的物理性被迫休眠,而小种子除物理性休眠外,可能还存在其他形式的深度生理休眠。准噶尔无叶豆自然状态下萌发率极低(≤3%),经综合分析,认为种子硬实和深度生理休眠可能是自然状态下种子萌发的困难主要因素,而土壤的光照、温度及湿度不存在明显的对种子萌发的限制。     

光照、温度及盐分对钠猪毛菜种子萌发的影响

通过对不同光照、温度条件下钠猪毛菜种子萌发实验及在光暗交替、15～25℃的最佳萌发条件下盐胁迫对无果翅种子萌发影响的实验研究,结果表明:光照对钠猪毛菜种子萌发有促进作用,对有果翅的种子萌发影响极其显著;温度是影响种子萌发的重要生态因子,种子萌发适宜温度较高,最适变温为15～25℃,萌发率在90%以上,亚适宜变温为5～25℃;果翅对种子萌发具有抑制作用;无果翅种子最终发芽率和发芽指数与NaCl溶液浓度呈显著的负相关关系,NaCl盐溶液浓度达1000 mmol/L时,最终发芽率为29.17%,发芽指数为3.07,与其他盐生植物相比,钠猪毛菜表现出极强的耐盐性,其种子萌发特性体现出对于盐生环境的适应性.     

几种旱生灌木种子萌发特性及化学成分

研究了旱生灌木白沙蒿(Artemisia sphaerocephala)、红砂(Reaumuria soongorica)、梭梭(Haloxylon ammodendron)、羊柴(Hedysarum mongdicum)、霸王(Zygophyllum xanthoxylum)、白刺(Nitraria tangutorum)、沙冬青(Ammopiptanthus mongolicus)、柠条(Caragana korshinskii)种子的化学成分、适宜发芽条件下的吸水发芽特性及两者之间的关系,测定和计算了其发芽率、吸水率,淀粉、脂肪、蛋白质、碳(C)、氮(N)、磷(P)含量及C:N、C:P、N:P值,并分析了这些指标间的相关性,以期归纳出西北干旱荒漠区植物种子萌发适应干旱环境的基本特性。结果表明:脂肪含量、蛋白质含量、氮含量与种子的最低萌发需水量之间呈显著正相关,而种子的单一化学成分及C:N、C:P、N:P值并没有对发芽率形成显著影响。8种植物种子萌发对环境的适应机制大致可分为两类:需要外界较高水分供应,萌发迅速而集中;不需要外界较高水分的供应,萌发持续而分散。     

九寨沟林下28种乡土观赏植物种子基本特征

为了筛选九寨沟旅游退化地段林下植被恢复的适宜物种,并揭示乡土植物种子基本性状特征,研究了九寨沟28种观赏性乡土植物种子基本特征 (长宽、种皮厚度、千粒重、活力、萌发率)以及低温层积提高种子发芽能力的作用.调查研究结果是:1) 28种植物种子中4种为小种子(<1 mg),53.6%是中等大小的种子(1～9.9 mg),32.1%为大种子(>9.9 mg).小种子均出现萌发,与小种子相比,种子休眠普遍存在于中等大小和大的种子中.2) 77%的物种种子活力较高(>72%),但仅有7种常规条件下能萌发;窄叶鲜卑花的萌发率最高,达到80%左右,6种植物的萌发率3%～50%.3)低温层积显著提高了蔷薇、毛果铁线莲、宽叶旌节花、假升麻的萌发率(P<0.05),也相对较早地提高了陇东海棠、鲜黄小檗、独活的萌发,但对大多数种子萌发没有促进作用.综合分析表明,九寨沟28种林下或林缘乡土植物中只有窄叶鲜卑花、毛果铁线莲、宽叶旌节花、假升麻、陇东海棠、鲜黄小檗、蔷薇等12种可直播或通过低温层积处理后直播用于旅游干扰退化地段的林下植被恢复中,而其他种类尚需进一步寻求打破休眠的措施和方法.     

模拟沙地干旱环境研究电场对两种沙生植物抗旱性的影响

用不同电场条件处理沙生植物柠条（Caragana intermedia）和沙蒿（Artemisia songarica Schrenk）种子,采用人工模拟干旱试验方法,研究电场处理后这两种植物种子萌发和生物量对土壤干旱胁迫的响应。结果表明,电场处理缓解了两种植物随干旱程度加重出现的负效应,不同处理条件,种子萌发和生物量对干旱胁迫的适应性的影响不同,电场处理能够提高种子在干旱胁迫条件下的发芽率和发芽势,提高两种沙生植物生物量干重和鲜重。这些变化缓解了干旱胁迫对柠条和沙蒿种子的伤害,提高了对干旱胁迫的适应性。     

浸种和冷冻处理对7种多年生泥炭沼泽植物种子萌发的影响

为了探讨泥炭沼泽多年生植物种子萌发的阻碍因素,研究了浸水和冷冻处理对7种沼泽植物种子萌发的影响。结果表明,在4种处理下,败酱(Patrinia scabiosaefolia)种子都保持相对高的萌发率,小白花地榆(Sanguisorba parviflora)次之,而鳞苞针蔺(Trichophorum alpinum)种子却都未萌发;在浸水处理下,小星穗薹草(Carex angustior)、臌囊薹草(Carex schmidtii)和山梗菜(Lobelia sessilifolia)种子的萌发率和萌发速率都显著提高,说明浸水处理能促进沼泽植物种子的萌发。在浸水处理下,细花薹草(Carex tenuiflora)种子的萌发率最高,其次为小星穗薹草,臌囊薹草种子的萌发率最低。浸水冷冻处理和浸提液冷冻处理都显著降低了沼泽植物种子的萌发率、萌发速率,并显著延长了种子的初次萌发时间。种子在浸水后遭遇冷冻环境可能是北方泥炭沼泽植物种子天然更新的阻碍因素之一。     

多年生人工草地对沙质土壤呼吸作用的影响

 在鄂尔多斯沙地改良试验站的撂荒地和退耕地,测定和分析了多年生人工草地对土壤呼吸速率的影响。结果表明,撂荒地上建植人工草地后土壤呼吸速率明显增高,人工建植草地土壤呼吸速率与撂荒地的土壤呼吸速率差异达到极显著水平(P<0.01);建植于退耕地上的无芒雀麦草地的土壤呼吸速率略高于玉米地土壤呼吸速率。撂荒地和退耕地上建植的无芒雀麦草地土壤呼吸速率高于冰草草地土壤呼吸速率。而施有机肥会提高人工草地的土壤呼吸。     

古尔班通古特沙漠南缘32种藜科植物种子萌发策略初探

对古尔班通古特沙漠南缘32种藜科植物的萌发特性（萌发率、萌发开始时间、平均萌发时间和萌发持续时间）进行研究,以探讨藜科植物的不同萌发对策及其生态适应意义。结果表明,32种植物萌发率呈双峰型,其中萌发率大于80%,或小于20%的种占大多数;萌发开始时间呈单峰型,28种植物在1~3 d内开始萌发;平均萌发时间也呈单峰型,平均萌发时间小于5 d的植物21种,最大的为杂配藜（23.7 d）;萌发持续时间种间差异较大,其中15种植物萌发持续时间小于15 d,10种植物持续时间在15~30 d,5种植物大于30 d。主成分分析和聚类分析结果表明,32种植物可划分为4种萌发类型:爆发型、过渡型、缓萌型和低萌型。以上结果揭示出32种藜科植物种子萌发策略不尽相同,表现为机会主义萌发策略、下注萌发策略和谨慎萌发策略,这与植物所处土壤盐渍化程度存在差异有关。此外,Log尺度下32种藜科植物种子大小及其变异范围较小（10-2~101）,暗示多数藜科植物多为小种子,其容易沿缝隙进入土壤形成短暂或永久种子库,这也是沙漠植物生存策略的重要一环。     

Seed germination of Southern Chihuahuan Desert plants in response to elevated temperatures

High temperature is one of the main factors that prevent germination, through premature aging of the embryo. The high temperatures reached in the soil of arid environments can affect seed survival and plant establishment. In this study we tested whether seed exposure to high temperature (40 °C and 70 °C) affected germination of eight species common to the Southern Chihuahuan Desert, and used for fodder, firewood and timber, fiber, edible flowers, fruits and stems. The responses to heat varied between species. Two of the tested species were not affected by heat exposure; for two other species germination was higher, and for the remaining four, germination was lower. There was also a delay of germination after heat exposure. Seeds of three species germinated >1 d slower after exposure to high temperatures. These results could help establish management programs for these Chihuahuan desert species under a climate change scenario.     

Seed germination of five mountain steppe species of Central Asia

This paper presents data on the germination traits of five perennials (Allium polyrrhizum, Agropyron cristatum, Arenaria meyeri, Artemisia frigida and Artemisia santolinifolia) widespread in the mountain steppes of southern Mongolia. Germination and seed viability were assessed at three alternate temperatures (8/4 °C, 20/10 °C, 32/20 °C), three levels of osmotic stress (deionized water; −0.5 MPa, −1 MPa Mannitol solution), and under conditions of alternate light/darkness versus complete darkness. The results of a factorial ANOVA with treatments and species as main effects showed that all five species germinated best at higher temperatures, with only Agropyron cristatum showing some seed mortality. Osmotic stress reduced seed viability and total germination in all five species. Darkness had no influence on viability, but positively affected seed germination of Allium polyrrhizum and Agropyron cristatum. We therefore conclude that, in the field, germination of all five species is mainly controlled by ambient temperatures and water availability, both of which drop towards the end of summer when dispersal takes place and effectively delay seedling recruitment until the next vegetation period.     

Reproductive and recruitment traits as indicators of the invasive potential of Kalanchoe daigremontiana (Crassulaceae) and Stapelia gigantea (Apocynaceae) in a Neotropical arid zone

Populations of two ornamental exotic species, Kalanchoe daigremontiana and Stapelia gigantea, have been recently detected inside a protected area containing arid ecosystems in Venezuela. We indirectly tested their invasive potential by characterizing their reproductive biology and recruitment patterns and comparing our estimates against Baker's Law and reproductive profiles reported for invasive plants. K. daigremontiana is autogamous, produces >16,000 seeds per plant and also reproduces clonally. Despite low seed viability (17.9%) and germination rates (11.9%), seeds were present in the seed bank. Plantlets of asexual origin showed high survival (75–100%) compared to seedlings of sexual origin (10%). S. gigantea is self-incompatible, xenogamous and produces close to 1500 seeds per m² of plant tissue. Seed viability (77%) and germination rates (62%) were high, but this species is not represented in the seed bank. It has a vegetative growth. A combination of reproductive and recruitment attributes, which match those considered in Baker's Law and others reported for invasive plants, confer K. daigremontiana and S. gigantea the potential to invade Neotropical arid zones; the former mainly through selfing and production of numerous asexual plantlets, and the latter through an association with a locally abundant pollinator and production of wind dispersed seeds.     

Germination in tamaulipan thornscrub of north-eastern Mexico

In semi-arid environments plants should be selected to germinate at times most suitable for seedling establishment. Germinability, rate of germination and temperature preference for germination (12 or 28°C constant) were analysed with respect to growth form (grass, forb, woody), longevity and seed size. Short-lived species showed preferential germination at either high or low temperature, whereas long-lived species tended to be indifferent to season. Germinability was >20% for 28 spp., 17 species were <10% and 21 species did not germinate under any circumstances. Growth form or life-span did not influence germination. Woody species germinated rapidly. Germinability and germination rate were positively associated.     

Photo-thermal regulation of seed germination in natural populations of Eruca sativa Miller (Brassicaceae)

Populations of the winter annual Eruca sativa in Israel are distributed along a climatic gradient, from Mediterranean mesic habitats in the north to semi-arid and arid habitats in the south. Seed cohorts of five populations sampled across the gradient were produced in a common-garden experiment, and their germination was tested under continuous light or darkness at 5–35 °C, as well as with alternating 30/20 and 25/15 °C temperatures under a 12/12 h photoperiod. Germination was enhanced by light and by increasing temperature. Under constant temperatures maximal germination of arid and semi-arid populations was lower than in the mesic populations, suggesting on higher levels of primary dormancy with increasing aridity. Seeds that did not germinate in darkness or at low temperatures in light, germinated almost fully when exposed to GA₃ at 25 °C, indicating that imbibition under less favorable conditions induces secondary dormancy in E. sativa. Daily alternating temperatures did not affect or even reduced seed germination compared to constant 25 and 30 °C in continuous light. Exposure of dry seeds to 30 °C before imbibition increased germination to ≥80% in seed cohorts of all populations. These responses to light and temperature indicate that adaptation of E. sativa to the Mediterranean environment is associated with the ability to germinate under the relatively warm autumn temperatures, and is enhanced by exposure to high temperature during the dry summer.     

Factors influencing seed germination of Cyperus capitatus, inhabiting the moving sand dunes in southern Europe

Cyperus capitatus Vandelli (Cyperaceae) is distributed in coastal sandy habitats and mobile dunes of south Europe. Its seed germination ecology is not known, despite its potential to be used in re-vegetation projects. Laboratory experiments were conduced to assess the effects of salinity, light regime, cold stratification and burial on seed germination of this species. Overall, increasing salinity delayed germination, increased seed dormancy and mean time to germination (MTG), and reduced final germination percentage, inhibiting it completely above 1% of salinity; although it did not affect seed viability. C. capitatus seeds exhibited their greatest germination at levels between 0 and 1% in non-stratified seeds, and between 0 and 0.5% for stratified seeds. Thus, the effect of salt was greater for stratified seeds at 5 °C. Germination in light/darkness conditions was similar to that in full darkness. Finally, burial in sand of C. capitatus seeds appeared to have a significant effect on cumulative percentage of germination. Seeds buried at depths greater than 2 and 3 cm showed a lower germination success than those on sand surface or buried at shallower depths. Burial also affected the beginning and speed of seed germination.     

生物土壤结皮与种子附属物对4种荒漠植物种子萌发的交互影响

生物土壤结皮能直接或间接地影响维管植物种子萌发与群落建成,种子本身的生物学特征（如种子附属物等）对萌发也存在一定影响。本研究选取古尔班通古特沙漠4种常见的具有不同形态附属物的藜科植物（梭梭（Haloxylon ammodendron ）、粗枝猪毛菜（Salsola subcrassa ）、心叶驼绒藜（Ceratoides ewersmanniana ）和角果藜（Ceratocarpus arenarius ））种子,设置苔藓结皮、地衣结皮和裸沙3种土壤基质,通过去除或保留种子附属物,对比研究了生物土壤结皮与种子附属物对种子萌发的影响。结果表明：粗枝猪毛菜和梭梭的苞片显著抑制了种子萌发（p <0.05）,心叶驼绒藜的柔毛和角果藜的刺状附属物对种子萌发没有显著影响（p >0.05）。与裸沙相比,苔藓结皮显著抑制了4种植物种子的萌发（p <0.05）,地衣结皮显著抑制了粗枝猪毛菜种子的萌发（p <0.01）,而对其他3种植物种子的萌发无显著影响（p >0.05）。同时,附属物与结皮对粗枝猪毛菜种子的萌发还具有交互作用,表现为显著抑制种子萌发（p <0.01）。可见,生物土壤结皮对具有不同附属物的荒漠植物种子萌发具有不同的影响,进而造成维管植物种子萌发的空间异质性,影响维管植物分布和多样性。