长三角及邻近地区138种草本植物DNA C-值测定及其生物学意义

为了评估DNA C-值和基因组大小(genome size)在植物入侵性评估中的价值,应用流式细胞仪测定了长三角及邻近地区138种草本植物的核DNA含量,其中111种为首次报道。在此基础上比较了不同植物类群这两个值的差异,特别是入侵性与非入侵性植物这两个值的差异。结果表明:(1)138种草本植物平均DNA C-值为1.55 pg,最大者是最小者的37.17倍。127个类群平均基因组大小为1.08 pg,最大者是最小者的34.11倍;(2)统计了菊科(Asteraceae)、禾本科(Poaceae)、石竹科(Caryophyllaceae)、十字花科(Brassicaceae)、玄参科(Scrophulariaceae)、蓼科(Polygonaceae)、唇形科(Labiatae)和伞形科(Umbelliferae)的DNA C-值和基因组大小,发现禾本科植物的这两个值显著地大于其他7个科(P0.01)。单子叶的DNA C-值和基因组极显著地大于双子叶植物(P0.01);(3)杂草比非杂草具有更低的DNA C-值(P0.01)和基因组大小(P0.001);与DNA C-值相比,基因组大小在这两个类群之间的差异更为明显(P0.001),这种现象也体现在菊科植物中。随着基因组(X1)和DNA C-值(X2)由大变小,植物的杂草性(入侵性,Y)由弱变强,两者关系分别符合:Y=2.2334-1.2847 ln(X1)(r=0.4612,P0.01)和Y=2.4421-0.7234 ln(X2)(r=0.2522,P0.01),DNA C-值和基因组大小可以作为植物入侵性评估的一个指标;(4)多倍体杂草的基因组极明显地小于二倍体杂草(P0.01),前者为后者的0.63倍。在非杂草中,多倍体基因组比二倍体的略小,前者仅为后者的0.84倍,差异不显著(P0.5)。菊科植物中多倍体杂草的基因组也显著地小于二倍体杂草(P0.1)。基因组变小和多倍体化相结合,进一步增强了植物的入侵性。在多倍体植物入侵性评估中,基因组大小比DNA C-值更有价值。     

紫茎泽兰叶片水浸液对蚕豆的化感效应

外来入侵植物可以通过淋溶、自然挥发、根系分泌和植株凋落物分解等途径向周围环境释放化感物质,抑制伴生植物的生长、发育。该研究以不同浓度紫茎泽兰(Eupatorium adenophorum)叶片水浸液处理蚕豆(Vicia faba)种子,研究紫茎泽兰叶片水浸液对蚕豆根尖细胞微核、染色体畸变、细胞凋亡、蚕豆幼苗叶片叶绿素和N含量、光合生理特性、生物量的影响。结果表明:(1)紫茎泽兰叶片水浸液处理显著抑制蚕豆根尖的伸长和细胞的有丝分裂,并诱导蚕豆根尖细胞染色体畸变和细胞微核的产生,有丝分裂指数随着叶片水浸液浓度增加而减小,根尖细胞微核率随叶片水浸液浓度增加而增大,高浓度叶片水浸液处理对蚕豆根尖细胞的凋亡及坏死有明显影响。(2)紫茎泽兰叶片水浸液处理引起蚕豆幼苗叶片的叶绿素和N含量显著降低,并导致蚕豆幼苗最大净光合速率和生物量的显著下降。总之,紫茎泽兰叶片水浸液可能引起蚕豆根尖的氧化损伤和抑制根尖的伸长,且叶片水浸液的抑制作用呈现一定的剂量效应。紫茎泽兰叶片水浸液对蚕豆根尖的损伤和抑制作用可能影响了植株对氮素的吸收,进而对蚕豆幼苗光合生理表现以及生物量积累产生显著负面效应。     

DNA C-值与被子植物入侵性关系的数据统计分析——以中国境内有分布的539种被子植物为例

统计了中国境内有分布的539种被子植物的DNA C-值,分析了它们在不同分类群、生活型、倍性、生活史类型以及在杂草和非杂草类群中的分布情况,主要结果如下:(1)539种被子植物DNA C-值平均为4.06 pg,其中木本植物的DNA C-值平均为1.84 pg,低于草本植物的平均值(5.02 pg);(2)双子叶植物(360种)的DNA C-值平均为2.20 pg,极明显地小于单子叶植物(179种)的平均值(7.80 pg);(3)1年生植物的DNA C-值平均为2.78 pg, 明显小于多年植物的平均DNA C-值(6.65 pg);(4)134种杂草的DNA C-值平均为1.93 pg,明显小于非杂草草本植物的平均值(6.75 pg),含杂草较多的科,平均DNA C-值相对较小;(5)统计的47种入侵杂草的DNA C-值平均为1.76 pg, 略小于134种杂草的平均DNA C-值(1.93 pg),极显著地小于非杂草性草本植物(6.75 pg);(6)以科为单位,不同科的DNA C-值存在着极大的差异;(7) DNA C-值与染色体倍性的关系并不明显,但是,随着倍性的增加,基因组变小;(8) 在同一科、属中,与非杂草相比,典型杂草的DNA C-值往往偏小;(9)总体上杂草或杂草性强的植物,它们的DNA C-值比非杂草性植物的要小.但是,也还存在一些例外,例如野燕麦(Avena fatua)的DNA C-值就高达14.15 pg,而相反,十字花科和葫芦科的一些非杂草栽培植物,却具有很低的DNA C-值.结论:DNA C-值在预测外来物种的入侵性方面具有一定的应用价值,但是,由于在木本植物和草本植物之间、单子叶与双子叶植物之间、一年生和多年生植物之间,特别是在不同的科之间,植物的DNA C-值较明显的差异,因此,根据DNA C-值预测外来物种的入侵性,应该严格地限于同一科(或属)内的相关物种间的比较.     

论DNA C-值与植物入侵性的关系

外来植物的入侵已引起世界普遍关注,强调并迅速提高对外来植物的预警能力是目前首当其冲的任务,由此,如何预测植物的入侵能力,也就成为入侵生态学的一个核心问题。20世纪90年代以来,关于植物入侵争论的焦点集中于入侵植物本身的生物学特点或入侵生境特点,然而,争议多于结论,至今未能找出有效预测外来植物入侵性的答案。着重从DNAC-值与植物入侵性关系这一角度进行论述。自20世纪30年代以来,染色体数目、大小、倍性在细胞水平的变化被认为可能与植物入侵性相关,因为染色体数目、大小变化是物种在细胞水平上的一种表型变异形式,而细胞水平累积的效应有可能决定着植物整体水平上对环境的适应能力,从而决定植物的分布范围,最终与入侵性相关。但是,这些领域的研究也没有得到一致的结论。近年来,人们将注意力转移至被子植物DNAC-值变化在植物环境适应中的生物学意义。现有资料表明,DNAC-值与细胞大小、体积、重量、发育速率等细胞水平上的表型特征存在正相关关系,这些与核型相关的DNAC-值的影响效应,可扩展到多细胞植物有机体的发育速率,在植物生活史的各个阶段起作用,其中就影响到两个受时间因子限制同时又与植物分布相关联的特征——最短世代时间及生活周期类型,而许多入侵成功植物即表现为世代时间短等特点,对于入侵性植物,其不可避免会受生长时间及分布环境的限制,如能保证其在这两方面占有优势便能入侵成功。已有研究结果表明,某些外来入侵种比同属其它种类具有较低的核DNA含量,由此,提出通过研究植物DNAC值,就有可能预测植物入侵能力的强弱,低DNAC-值的植物具有更强的适应环境的能力,即与入侵性大小呈负相关,这为发现新的植物入侵性预测指标提供了思路。     

干扰强度对群落中紫茎泽兰种子萌发、幼苗定居和生长的影响

干扰与外来植物入侵密切相关,种子萌发和幼苗定居是植物生活史中最脆弱、也是外来植物入侵最关键的阶段.为研究干扰在恶性外来入侵植物紫茎泽兰成功入侵过程中的作用,采用人工牧草群落代替自然群落,人为干扰(去除不同面积的牧草)模拟自然干扰的方式,研究了紫茎泽兰入侵初期种子萌发、幼苗定居和生长对不同干扰强度的响应与适应.结果表明:...     

植物种子大小与幼苗生长策略研究进展

种子大小和幼苗更新对策是植物生活史策略的重要组成部分.本文从不同侧面综述了当前国内外关于种子大小和幼苗之间关系的生态学研究,包括:种子大小对萌发出土的影响,种子大小与幼苗形态生长特性之间的关系,种子大小与幼苗存活、竞争能力之间关系等,并对今后的相关研究进行了展望.在不同的微环境和植被类型下,种子大小与幼苗生长之间的关系可能有所差异;种子大小对植物幼苗生长的影响导致种子大小不同的植物对植被幼苗更新补充的贡献不同;种子大小与幼苗生活史策略关系在大尺度的群落空间水平上和小尺度的物种间与物种内的研究对于天然植被的更新恢复研究具有重要意义.     

不同光照处理下青藏高原克隆植物黄帚橐吾(Ligulariavirgaurea)种子大小对其幼苗生长的影响

以高寒草甸克隆植物黄帚橐吾为实验材料,通过遮荫网模拟植被遮荫,研究种子大小与萌发及幼苗生长能力的关系和幼苗对光照条件的反应。结果表明:(1)在自然光照下,黄帚橐吾种子大小对种子萌发的影响显著,大种子的萌发率高于小种子。遮荫生境下,大、小种子萌发率有所降低,但遮荫对小种子萌发的影响比大种子显著。小种子的萌发率下降了近1/8,而大种子的萌发率仅下降了1/11。(2)黄帚橐吾种子大小对幼苗生物量积累影响显著,大种子幼苗总生物量(TB)大于小种子幼苗的。但生物量的分配与播种时间相关,播种后60d,在自然光照条件下,大种子幼苗对根生物量的分配大于小种子幼苗,而对叶生物量的分配则正好相反。在遮荫环境中,大、小种子幼苗普遍对根的生物量分配增加,大种子幼苗根冠比(R/S)大于小种子幼苗。(3)黄帚橐吾种子大小对幼苗的生长也有明显影响。在自然光照下,小种子幼苗的相对生长速率(RGR)较大于大种子幼苗,但叶面积比率(LAR)、叶面积干质量比(SLA)、叶干质量(LWR)差别不明显。在遮荫条件下,幼苗的LAR、SLA、LWR显著增加,但大、小种子幼苗间差异不显著,幼苗的RGR减小,小种子幼苗的减小趋势大于大种子幼苗。     

空间条件对植物细胞和亚细胞器的影响

空间条件对细胞核的影响是各种各样的。松树苗的细胞核数量减少,小麦核体积增大。缩合染色质体积增加,降低了它的功能,也影响了蛋白质合成。空间生长的豌豆、黄瓜幼苗中内质网的潴泡减少,水芹的内质网增多。玉米幼苗线粒体内膜序性降低,体积膨胀,但玉米根冠细胞中的线粒体体积比地面的减少31％。豌豆根分生组织中的高尔基体在失重下其潴泡形态有变化。在微重力下玉米根冠的高尔基体比对照少50-     

不同光强下入侵植物剑叶金鸡菊与伴生种生长和光合特征研究

研究了剑叶金鸡菊及其伴生植物鬼针草、羊蹄幼苗的生物量分配、生长和生理特性在不同强度的光生境中(全光照和31％光照)的响应特征,探讨了这些特征与其入侵性的关系.结果表明:(1)光强是影响剑叶金鸡菊入侵的重要环境因子,高光环境下其幼苗较高的相对生长速率( RGR)和植物单位重量的光合效率(Am)与其入侵性密切相关.遮荫下,...     

除草通对玉米幼苗根尖细胞有丝分裂的影响

本文研究了除草通对玉米幼苗初生不定根根尖细胞有丝分裂的影响。结果表明,除草通是一种影响细胞有丝分裂的除草剂,其作用方式在于阻止分生组织细胞从前期向中、后、末期的过渡,引起染色体凝集、短缩以及多核、多核仁等一系列畸形与异常变化。     

Adaptive traits of wild barley plants of Mediterranean and desert origin

Reciprocal introduction of seeds and seedlings was used to test for local adaptation and to identify a set of co-adapted traits of Mediterranean and desert ecotypes of wild barley Hordeum spontaneum. Evidence for local adaptation was found in seedling introductions into intact environments and from ecotype colonization success in the first generation after seed dispersal. Estimates of fitness were obtained at particular stages of the life cycle (seed, seedling and adult). Experiments that manipulated the environment (vegetation removal, different plant density) demonstrated the intensity and direction of natural selection in different life history episodes, but there was no strong evidence for local adaptation under these circumstances. The observed genetically determined differences between Mediterranean and desert ecotypes can be summarized as the following: reproductive output was higher in desert plants, with smaller seeds than in Mediterranean plants. There was a higher competitive ability of Mediterranean than desert plants. Plants of desert origin had significant reductions in yield when grown in mixed stands with Mediterranean plants; no such effect was observed for plants of Mediterranean origin. Seed germination and seedling survival was lower in seeds of desert origin. This was due to both: genetically determined higher dormancy of desert seeds and a trade-off between no. of seeds and their size (directly related to seed/seedling vigour).     

Seed size influences arbuscular mycorrhizal symbiosis across leguminous host-plant species at the seedling stage

Eighteen species of the Fabaceae were selected to investigate the relationship between plant seed size and the density of arbuscular mycorrhizal (AM) structures on the roots of young plants. The results demonstrated that seed size showed a strong negative correlation with the density of AM structures: smaller seeds exhibiting higher AM densities, which suggested that seed size may regulate AM symbiosis across leguminous host-plants species in natural habitats. Furthermore, the results also implied that different plant species used specific strategies, such as mycorrhizal symbiosis, to enhance seedling survival at the seedling stage.     

Irrigation and fertilization effects on seed number,size, germination and seedling growth: implications for desert shrub establishment

Plants with limited resources adjust partitioning among growth, survival, and reproduction. We tested the effects of water and nutrient amendments on seed production, size, and quality in Sarcobatus vermiculatus (greasewood) to assess the magnitude and importance of changes in reproductive partitioning. In addition, we assessed interactions among the environment of seed-producing plants (adult plant scale), seed size, and seedling microenvironment (seedling scale) on successful seedling establishment. Interactions of these factors determine the scale of resource heterogeneity that affects seedling establishment in deserts. Both total number of seeds produced per plant and seed quality (weight and germination) increased significantly in the enriched treatment in a 3-year field experiment. Seedling length 3 days after germination and seed N concentration, other measures of seed quality, were higher for seed from both irrigated and enriched plants than for seed from control plants. Field S. vermiculatus seed production and quality can be substantially increased with irrigation and nutrient enrichment at the adult plant scale and this allows management of seed availability for restoration. However, based on a greenhouse study, seedling environment, not the environment of the seed-producing plant or seed size, was the most important factor affecting seedling germination, survival, and growth. Thus it appears that production of more seed may be more important than improved seed quality, because higher quality seed did not compensate for a low-resource seedling environment. For both natural establishment and restoration this suggests that heterogeneity at the scale of seedling microsites, perhaps combined with fertilization of adult shrubs (or multi-plant patches), would produce the greatest benefit for establishing seedlings in the field.     

Seedling disease in an annual legume: consequences for seedling mortality, plant size, and population seed production

The effect of seed and seedling mortality on plant population dynamics depends on the degree to which the growth and reproduction of surviving individuals can compensate for the deaths that occur. To explore this issue, we sowed seeds of the annual Kummerowia stipulacea at three densities in sunken pots in the field, which contained either field soil, microwaved field soil, or microwaved field soil augmented with oospores of three Pythium species. High sowing density reduced seedling establishment and seedling size, but these effects were independent of the soil treatment. In the oospore-augmented soil, seed and seedling survival was low. The surviving plants were initially smaller but, at maturity, average plant size was greatest in the oospore-augmented soil, compared to the other treatments. Total population seed production was unaffected by soil treatment, suggesting that the effect of disease was limited to the seedling stage, with surviving plants released from intraspecific competition. To test the hypothesis that the surviving plants in the oospore-augmented soil were more disease-resistant, seeds from each of the sowing density-soil type treatments were sown in a growth chamber inoculation study. No evidence for selection for resistance was found. A second inoculation experiment revealed that oospore inoculum reduced plant numbers and mass regardless of whether field or microwaved soil was used, suggesting that results from the field experiment were not dependent on the use of microwaved soil. The findings of this study indicate that the ecological effects of disease on individual plants and on plant populations are not necessarily equivalent. Received: 13 January 1999 / Accepted: 21 September 1999     

Seed mass versus seedling performance in Scots pine: a maternally dependent trait

It is generally accepted that larger seeds give rise to seedlings with better performance. On the other hand, the size that a seed reaches is genetically determined by at least two different traits ; the genetic variability of the developing embryo and the genetic variability of the maternal plant. Thus, the relative contributions of these two traits affect seedling performance by influencing seed size. In this paper, I investigate the effect of seed size on seedling performance in the Scots pine ( Pinus sylvestris ). From eight maternal plants, 50 seeds were planted in each of two soil types (800 seeds in total), and seedling performance was monitored for 1 yr. Seed mass proved to be highly constant within maternal plants. Soil type influenced emergence and survival; however, the effect of soil type differed depending on maternal origin. Seed mass was positively correlated with seedling emergence, although this relationship was not found for seedling survival or date of emergence. The initial growth of the shoot was also positively correlated with seed mass. However, after one growing season, seed mass had no effect on seedling performance, which depended exclusively on maternal origin. Nevertheless, the mean mass of seeds produced by plants was positively correlated with mean values of growth parameters. Thus, first-year seedling performance seems to be a maternal trait indirectly associated with seed size.     

Seed size, seedling morphology, and response to deep shade and damage in neotropical rain forest trees

To investigate the existence of coordinated sets of seedling traits adapted to contrasting establishment conditions, we examined evolutionary convergence in seedling traits for 299 French Guianan woody plant species and the stress response in a shadehouse of species representing seed size gradients within five major cotyledon morphology types. The French Guianan woody plant community has larger seeds than other tropical forest communities and the largest proportion of hypogeal cotyledon type (59.2%) reported for tropical forests. Yet the community includes many species with intermediate size seeds that produce seedlings with different cotyledonal morphologies. A split-plot factorial design with two light levels (0.8% and 16.1% PAR) and four damage treatments (control, seed damage, leaf damage, stem damage) was used in the shadehouse experiment. Although larger-seeded species had higher survival and slower growth, these patterns were better explained by cotyledon type than by seed mass. Even larger-seeded species with foliar cotyledons grew faster than species with reserve-type cotyledons, and survival after stem grazing was five times higher in seedlings with hypogeal cotyledons than with epigeal cotyledons. Thus, to predict seedling performance using seed size, seedling morphology must also be considered.     

Seed size as an indicator of seed quality: a case study of Primula veris

Seed size is a widely accepted measure of seed quality, because many earlier studies have shown that large seeds have high seedling survival, growth and establishment. We tested whether ovule loss increases size of the remaining seeds and whether such size increase affects seedling establishment. We removed all except one flower from inflorescences of Primula veris L. (Primulaceae), a perennial hemicryptophyte herb, at a late stage of flowering. Flower removal (FR) increased seed size by 33% compared to the control plants. We then divided the seeds within each treatment to small, middle-sized and large seeds and carried out a sowing experiment in the field. Within each experimental group, seedling establishment was positively associated with seed size. However, despite size differences, seeds from the FR and control groups had the same seedling establishment probability. Seeds from FR plants had a higher seedling emergence in May than those from control plants, but the number of seedlings alive per sowing plot in the late summer was the same in both experimental groups. Increase in seed mass after partial FR thus did not enhance seedling performance, although seed size variation due to other causes was positively correlated with seedling establishment. Further studies are needed to show whether plastic changes of seed size are usually adaptive or not.     

Seed size as an indicator of seed quality: a case study of Primula veris

Seed size is a widely accepted measure of seed quality, because many earlier studies have shown that large seeds have high seedling survival, growth and establishment. We tested whether ovule loss increases size of the remaining seeds and whether such size increase affects seedling establishment. We removed all except one flower from inflorescences of Primula veris L. (Primulaceae), a perennial hemicryptophyte herb, at a late stage of flowering. Flower removal (FR) increased seed size by 33% compared to the control plants. We then divided the seeds within each treatment to small, middle-sized and large seeds and carried out a sowing experiment in the field. Within each experimental group, seedling establishment was positively associated with seed size. However, despite size differences, seeds from the FR and control groups had the same seedling establishment probability. Seeds from FR plants had a higher seedling emergence in May than those from control plants, but the number of seedlings alive per sowing plot in the late summer was the same in both experimental groups. Increase in seed mass after partial FR thus did not enhance seedling performance, although seed size variation due to other causes was positively correlated with seedling establishment. Further studies are needed to show whether plastic changes of seed size are usually adaptive or not.