矮慈菇居群的数量分类研究

本文运用聚类分析和主成分分析基础上构造最小生成树的方法,对采自中国南方的7个矮慈菇居群用28个形态学性状进行了数量分类研究。结果划分出3个类群,综合反映了各居群间的亲缘关系。本文还简要讨论了数量分类学方法在居群生物学中的应用问题。     

福建野生单叶蔓荆子总黄酮与蔓荆子黄素含量分析

对福建省不同地区野生单叶蔓荆子总黄酮和蔓荆子黄素含量进行测定,不同地区含量差异进行比较分析,确定福建野生单叶蔓荆子的质量水平,为进一步开发福建野生单叶蔓荆子提供基础研究数据。回流提取总黄酮,紫外分光光度法(UV法)测定总黄酮含量,高效液相色谱法(HPLC法)测定蔓荆子黄素含量。结果表明不同产地野生单叶蔓荆子总黄酮含量范围为7.081%～10.792%,平均含量9.040%;蔓荆子黄素含量范围为0.06170%～0.12578%,平均含量0.08878%。福建省不同地区野生单叶蔓荆子质量(以蔓荆子黄素含量为指标)均符合药典规定,可进一步开发利用。     

小慈姑的遗传多样性和居群分化

小慈姑是中国南部狭域分布的易危水生植物。采用聚丙烯酰胺凝胶电泳和等位酶分析方法,研究了该种江西东乡、湖南茶陵、广西桂林和福建武夷山4个地点的8个自然居群的遗传分化及其与地理位置的相关性。9个酶系统18个等位酶位点的检测结果表明,小慈姑有较高水平的遗传多样性:多态位点百分率P=16.67%—38.89%,平均每位点等位基因数A=1.278—1.833,平均预期杂合度He=0.0941—0.1928,平均观察杂合度Ho=0.1461—0.2127。居群之间有较高的遗传一致度I=0.7161—0.9965。根据Nei s遗传距离所作出的聚类分析显示,同地居群之间有较紧密的遗传关系,居群间的遗传分化与空间距离呈正相关。     

Effects of aquatic macrophytes on organic matter deposition,resuspension and phosphorus entrainment in a lowland river

1. Although macrophytes play a key role in the structure and functioning of lowland rivers, most of the basic plant, hydrodynamic and sediment‐water interactions have only been described qualitatively. We therefore studied quantitatively, the seasonal dynamics of matter deposition and mobilisation inside and outside (free path) a representative patch of arrowhead, Sagittaria sagittifolia, in the lowland River Spree, NE Germany, in August 2006. Our in situ study combined resuspension experiments, a hydrodynamically calibrated erosion chamber and concurrent measurements of the prevailing flow characteristics and bed load. 2. Increasing entrainment rates (E) of particles (E_SPM) and total P (E_TP), with increments of shear velocity (U_*) from 0.53 to 2.42 cm s^?1, were significantly higher inside the plant patch than outside. Indeed, E_SPM and E_TP at the lowest U_* were 8‐ and 12‐fold higher inside than outside the patch, reflecting the resuspension potential of the upper nutrient‐enriched layer and the extent of pulsed P inputs even at small increases in U_*. 3. Vertical distribution of velocity (u) revealed a flow pattern of a mixing layer inside the S. sagittifolia patch, and that of a boundary layer in the free path. The highest gradient of u in the mixing layer was located in the water column at about 0.5 m depth, whereas the highest gradient of u for the boundary layer was found near the riverbed. The maximum of U_* (1.65 cm s^?1) was only 4 mm above the sediment. 4. A plant mosaic provides a low‐energetic environment promoting extensive particle trapping and the accumulation of a fine‐grained, nutrient‐enriched sediment, and forming a large resuspension potential. Consequently, after plant decay and the concomitant increase of U_* this material is preferentially entrained at higher rates. Hence, the key role of submerged macrophytes in lowland rivers is more directly related to modifying the dynamic equilibria between vegetation trapping and resuspension, than to the retention of nutrients, particularly P, and the reduction of P loads downstream to other waters.     

Gender variation of sequential inflorescences in a monoecious plant Sagittaria trifolia (Alismataceae)

In protogynous plants, female flowers of early blooming plants are at a reproductive disadvantage because they cannot set fruit due to the lack of available pollen. To study this phenomenon, gender expression of the monoecious herb Sagittaria trifolia was investigated over the entire flowering season in two field and two cultivated populations in Hubei and Hunan Provinces, China. In racemes of S. trifolia, flowers open sequentially from bottom to top, with female flowers opening first followed by male flowers. This creates a temporal separation of sexes in the species. Under field conditions small plants are often male, with production of both male and female flowers increasing with plant size. Femaleness increased among sequential inflorescences since female flower production increased whereas male flower production did not. Seed production was greater in large inflorescences because they contain more female flowers, and the number of ovules increased in female flowers at basal positions within the raceme. A consistent pattern of high seed set was observed in flowers from both field and cultivated populations. About 1 % of unfertilized ovules resulted from no pollination and 2 % of the seeds produced were only partly developed due to resource limitation. In the first inflorescence of the six experimental populations, 6.7-40.0 % of individuals produced only male flowers, and female flowers of 1.9-6.5 % individuals were aborted. The occurrence of male flowers in early blooming inflorescences could be an adaptive strategy to conserve resources and enhance pollination of female flowers in protogynous S. trifolia.     

Response of two oligohaline marsh communities to lethal and nonlethal disturbance

Severity is recognized as an important attribute of disturbance in many plant communities. However, the effects of disturbances of different severity on patterns of regeneration in oligohaline marsh vegetation have not been experimentally examined. In these communities, a critical difference in the effects of disturbance severity may be whether the vegetation dies as a result of the disturbance or is merely damaged and hence capable of resprouting. We described the regeneration of vegetation in two Louisiana marsh community types, one dominated by Sagittaria lancifolia L. and the other by Spartina patens (Ait.) Muhl., following three levels of disturbance: no disturbance, a nonlethal disturbance, and a lethal disturbance. In the nonlethal disturbance, aboveground vegetation was clipped to simulate common disturbances such as fire and herbivory that remove aboveground vegetation but leave rhizomes intact. In the lethal disturbance vegetation was killed using herbicide to simulate disturbances causing plant mortality such as wrack deposition, sedimentation, scouring, and flooding following fire or herbivory. Regeneration was assessed over a 2-year period by measuring plant species richness, relative abundance, relative dominance, cover, and final biomass. To elucidate mechanisms for observed responses of vegetation, the species composition of the seed bank, light penetration, water level, salinity, and soil redox potential were evaluated. Despite differences in the structure of undisturbed vegetation in the two community types, they exhibited the same overall pattern of regeneration. Following nonlethal disturbance, the dominant species resprouted and quickly reestablished the structure of the vegetation. In contrast, recolonization following lethal disturbance occurred primarily via seedling recruitment, which resulted in marked shifts in community structure that persisted throughout the study. While the two communities responded similarly overall to disturbance, the response of individual species was not uniform; abundance, dominance, biomass, or cover increased for some species but decreased for others in response to disturbance. Seed bank species occurred in the vegetation following lethal disturbance in the Spartina community and in both disturbed and undisturbed plots in the Sagittaria community, indicating that the seed bank is a source of propagules for regeneration and maintenance of oligohaline marshes. Of the environmental variables measured, light level was most closely related to the effect of disturbance severity on community structure. Our results suggest that lethal and nonlethal disturbances have differential effects on regeneration of vegetation that can create pattern in oligohaline marshes communities. Received: 29 September 1997 / Accepted: 12 May 1998     

Population genetics of two rare perennials in isolated wetlands: Sagittaria isoetiformis and S. teres (Alismataceae)

We investigated genetic structure in two closely related perennial plants that occur in isolated wetlands: Sagittaria isoetiformis, restricted to the southeastern Coastal Plain of North America, and S. teres, endemic to the northeastern Coastal Plain. Using horizontal starch-gel electrophoresis, we screened 527 individuals from 11 populations of S. isoetiformis and 367 individuals from seven populations of S. teres. A high proportion of the 16 loci were polymorphic (%P(S) = 93.8% in S. isoetiformis and %P(S) = 75.0% in S. teres), with higher mean numbers of alleles per polymorphic locus and effective alleles per locus in S. isoetiformis (AP = 3.27, A(E) = 1.90) than in S. teres (AP = 2.58, A(E) = 1.30). Species- and population-level expected heterozygosities were higher in S. isoetiformis (H(ES) = 0.399, H(EP) = 0.218) than in S. teres (H(ES) = 0.177, H(EP) = 0.101). Jackknife estimates of F statistics indicated moderate levels of inbreeding in S. teres (F(IS) = 23.1%). Strong differentiation characterized these geographically isolated populations (G(ST) = 39.9% in S. isoetiformis, and G(ST) = 26.1% in S. teres). Genetic identities varied substantially within (ī = 75%, range = 0.558-0.963 in S. isoetiformis; ī = 89%, range = 0.776-0.963 in S. teres) and among species (ī = 81%, range = 0.506-0.882), leading to the discrimination of four regional population clusters using nonmetric multidimensional scaling (NMDS). It appears that S. isoetiformis and S. teres are a progenitor-derivative species pair.     

利用SSR荧光标记对野慈姑异交率的估测

对自交亲和植物交配系统进行估测,有利于了解植物的繁殖状态、自异交进化的轨迹和特定种群的自然历史或选择压力。自交亲和的野慈姑有性繁殖和克隆繁殖并存,且其花序内和无性系分株间存在雌雄花同时开放的现象即给自交带来了机会。本研究利用SSR标记估测野慈姑自然种群的异交水平,并比较分析异交率估测中荧光定量法的准确性和优势,探讨野慈姑不同自然种群微卫星位点的多态性。结果表明,从28对SSR引物中筛选出3对多态性较高的引物,其多种群水平的位点数分别是5、6、6;对1个自然种群的6棵植株共计31个果实的异交率进行估测,其整体异交率为92.87%±2.5%,揭示了野慈姑自然种群的交配系统以异交为主,且无性繁殖对后代的贡献有限;单引物水平下,荧光定量技术检测出的多态性位点数和杂合率均高于NativePAGE成像电泳,且其对异交率估测的结果也更准确;另外,从检测效率实验耗时和实验成本等方面综合分析,本研究推荐使用荧光定量技术。     

野慈姑花粉限制评估的影响因素

以野慈姑为材料,研究补充授粉的处理水平(单花、花序)和花粉质量(自花花粉、异花花粉)对花粉限制评估的影响.结果表明: 补充授粉的处理水平会造成花粉限制的程度不同(P=0.0021),单花水平的授粉会导致花朵之间的资源重新分配,从而影响结实;补充授粉的花粉质量会对结实造成影响,补充异花花粉比自花花粉能产生更多的种子(P=0.0497),且萌芽率更高(P=0.0428),表明该体系的花粉限制不是数量的限制,而是优质花粉的限制.不同的试验水平和花粉质量可能对花粉限制的评估造成影响,相关研究应尽量对整个花序或者植株进行补充授粉,材料允许时还应考虑自异花粉的对比试验,有利于更客观地认识和检测花粉限制.