不同光强下单叶蔓荆的光合蒸腾与离子累积的关系

同步分析了生长在滨海滩涂沙地的灌木单叶蔓荆钠和钾离子的累积量与植物的水分累积消耗量与光合产物累积量的日变化特点和累积的关系,并比较了单叶蔓荆在晴天和阴天的木质部溶液离子浓度与植物水势的关系和水分利用效率的差别,结果表明:单叶蔓荆在光强度较高的晴天的水分利用效率高于阴天,在晴天的光合产物累积达到了阴天的约4倍,却只消耗了约为阴天3倍的水。随着植物体水势的降低,单叶蔓荆木质部溶液的钠离子的浓度和钾离子浓度呈降低趋势但不明显。木质部溶液的钾离子浓度和钾离子累积量无论在晴天和阴天都明显低于钠离子的浓度和累积量。单叶蔓荆的高浓度的钠离子吸收有可能在液泡累积并降低细胞的渗透势,增加细胞的吸水能力和植物的抗旱抗盐能力。     

宽叶泽苔草萜类化学成分分析及其化学分类学意义

宽叶泽苔草Caldesia grandis隶属泽泻科Alismataceae,是一种珍稀濒危水生植物。其化学成分迄今未见报道。本文利用气质联用的方法鉴定了该植物的43种化学成分,并总结了已报道的其近缘泽泻属Alisma、慈姑属Sagittaria、刺果泽泻属Echinodorus植物的化学成分,据此进行化学分类学分析:它们的特征化学成分是二萜,宽叶泽苔草和泽泻属植物的二萜成分是处于二萜生源合成途径最顶端的kaurane类型;慈姑属植物的二萜成分既有处于该途径底端的clerodane型、中间的pimarene型,也有顶端的kaurane型、abietene型二萜;刺果泽泻属植物的二萜成分是处于该途径底端的clerodane型。宽叶泽苔草和泽泻属植物都有桉叶烷型和愈创木烷型的倍半萜。因此宽叶泽苔草和泽泻属植物的亲缘关系比慈姑属、刺果泽泻属植物的近,由此推测它们的进化层次可能依次是刺果泽泻属植物、慈姑属植物、泽泻属植物、宽叶泽苔草。     

贵州泽泻科植物分布新记录—利川慈姑

以前报道中国特有种-利川慈姑(Sagittaria lichuanensis)仅仅分布在我国的福建、广东、江西三省交界的武夷山山脉以及湖北利川县,该种在贵州的分布为新记录.对该种的形态特征和群落特点作了介绍,同时还比较了该分布点与其它分布点之间生境条件的差异及分布格局.该种在贵州的分布使其地理分布状况从仅仅分布在我国的第三级阶梯变为分布于我国的第二、第三级阶梯.这一发现为研究慈姑属的地理分布规律以及系统演化历史提供了新的场所和证据.此外,该种独特的生殖特点为比较不同生境条件下物种的生殖策略差异提供了有利条件.     

野慈姑自然群体异交率的定量估测

用自然群体取样和同工酶遗传标记的方法对沼生植物野慈姑（Sagittaria trifolia Linn.）及其变型长瓣慈姑［S.trifolia Linn.f.longiloba(Turcz.)Makino］的异交率作了定量研究,3个自然群体的异交率估计值为=91.0％～98.0％,表明该种为异交占绝对优势的交配系统。在野慈姑各群体间未发现异交率的显著差异。 Abstract:The outcrossing rates of Sagittaria trifolia Linn.and S.trifolia Linn.f.longiloba(Turcz.) Makino,a helophyte species and a form under the species,were estimated by sampling from natural habitats and using isozyme locus as genetic marker.According to the values of outcrossing rates in 3 populations( =91.0％～98.0％),the mating system of the species studied was found to be dominated by outcrossing mechanisms.Statistical analysis suggested that there was no significant difference in outcrossing rates among the populations.     

冠果草的性表达状态及其进化含义

通常认为雄花两性花同株是植物性表达两性花进化到雌雄异株的过渡类型之一。慈姑属仅冠果草（Ｓａｇｉｔｔａｒｉａ ｇｕｙａｎｅｎｓｉｓ Ｈ．Ｂ．Ｋ．ｓｕｂｓｐ．ｌａｐｐｕｌａ（Ｄ．Ｄｏｎ）Ｂｏｊｉｎ）的性表达为典型的雄花两性花同株,其他种为雌雄同株。对冠果草野外和实验居群的性配置进行了定量观察。东乡和武夷山居群雄花的比例分别为２．４８％０．９６％。实验表明,栽培条件影响冠果草的性表达：在营养较好的条件下     

繁殖方式对矮慈姑生长的影响

矮葱姑的种子繁殖和球茎营养繁殖对植株生物量和高度都有明显的影响。种子繁殖苗生物量的增长曲线方程不同球茎繁殖苗的生物量增长曲线方程从生物量比较可见,在生长初期。球茎繁殖苗的生物量远大于种子繁殖苗。生长过程中,种子繁殖苗的生长速率大于球茎繁殖苗。在生长后期,二者生物量接近。种子繁殖苗的高度动态方程与球茎繁殖苗的高度动态方程也不一样。种子繁殖苗和球茎繁殖苗高度的增长速率在生长的前期均高于生长后期。     

Growth and energy status of arrowhead tubers,pondweed turions and rice seedlings under anoxic conditions

The responses of two aquatic plants, arrowhead (Sagittaria pygmaea Miq.) and pondweed (Potamogeton distinctus A. Benn), to anoxia were compared with those of rice (Oryza sativa L.). Shoot elongation of arrowhead tubers was enhanced at around 1 kPa O₂, whereas that of pondweed turions was slight in air and reached a maximum in the absence of O₂. Anaerobic enhancement of alcohol dehydrogenase (ADH) activity took place in rice coleoptiles but not in arrowhead and pondweed shoots. Shoots of both arrowhead and pondweed maintained a more stable energy status than did the rice coleoptile under anaerobic conditions. Total adenylate nucleotide contents of arrowhead and pondweed shoots were constant under anaerobic conditions. Adenylate energy charge in both shoots remained at a high and stable level of more than 0·8 for at least 8 d. Three forms of ADH from arrowhead shoots were separated by starch gel electrophoresis, showing that the activity of each ADH form was different under aerobic and anaerobic conditions. The incorporation of ³⁵S-labelled Cys and Met into soluble proteins in arrowhead shoots showed active protein biosynthesis and an involvement of a special set of polypeptides in the anaerobiosis.     

Vegetation differentiation in the patterned landscape of the central Everglades: importance of local and landscape drivers

Aim We present a model to account for self‐assembly of the slough–ridge–tree island patterned landscape of the central Everglades in southern Florida via feedbacks among landforms, hydrology, vegetation and biogeochemistry. We test aspects of this model by analysing vegetation composition in relation to local and landscape‐level drivers. Location We quantified vegetation composition and environmental characteristics in central Water Conservation Area (WCA) 3A, southern WCA‐3A and southern WCA‐3B in southern Florida, based on their divergence in water management and flow regimes over the past 50 years. Methods In 562 quadrats, we estimated species coverages and quantified maximum, minimum and average water depth, soil depth to bedrock, normalized difference vegetation index (NDVI) and proximity to the nearest tree island. We used non‐metric multi‐dimensional scaling (NMS) to relate compositional variation to local and landscape‐level factors, and evaluated environmental differences among eight a priori vegetation types via anova . Results Water depth and hydroperiod decreased from sloughs to ridges to tree islands, but regions also differed significantly in the abundance of several community types and the hydroregimes characterizing them. NMS revealed two significant axes of compositional variation, tied to local gradients of water depth and correlated factors, and to a landscape‐scale gradient of proximity to tall tree islands. Sawgrass height and soil thickness increased toward higher ridges, and NDVI was greatest on tree islands. Main conclusions This study supports four components of our model: positive feedback of local substrate height on itself, woody plant invasion and subsequent P transport and concentration by top predators nesting on taller tree islands, compositional shifts in sites close to tree islands due to nutrient leakage, and flow‐induced feedback against total raised area. Regional divergence in the relationship of community types to current hydroregimes appears to reflect a lag of a few years after shifts in water management; a longer lag would be expected for shifts in landscape patterning. Both local and landscape‐level drivers appear to shape vegetation composition and soil thickness in the central Everglades.     

Gender plasticity in Sagittaria sagittifolia (Alismataceae), a monoecious aquatic species

 Aquatic plants are well known for their high degree of phenotypic plasticity in vegetative structures, particularly leaves. Less well understood is the extent to which their sexuality can be modified by environmental conditions. Here we investigate gender plasticity in the European clonal monoecious aquatic Sagittaria sagittifolia (Alismataceae) to determine how floral sex ratios may vary with plant size and inflorescence order. We sampled two populations from aquatic habitats in East Anglia, U.K. and measured a range of plant attributes including ramet size and the number of female and male flowers per inflorescence. The two populations exhibited similar patterns of phenotypic gender, despite contrasting patterns of total allocation to female and male flower number. Plants produced male-biased floral sex ratios but female flower number increased from the first to the second inflorescence whereas male flower number decreased. Size-dependent gender modification occurred in both populations, but the patterns of allocation to female flower production differed between the two populations. Our results are consistent with the view that monoecy is a sexual strategy that enables plants to adjust female and male allocation in response to changing environmental conditions. Received September 16, 2002; accepted October 23, 2002 Published online: March 20, 2003     

Production of male flowers does not decrease with plant size in insect-pollinated Sagittaria trifolia, contrary to predictions of size-dependent sex allocation

It has been proposed that relative allocation to female function increases with plant size in animalpollinated species.Previous investigations in several monoecious Sagittaria species seem to run contrary to the prediction of size-dependent sex allocation (SDS),throwing doubt on the generalization of SDS.Plant size,phenotypic gender,and flower production were measured in experimental populations of an aquatic,insect-pollinated herb Sagittaria trifolia (Alismataceae) under highly different densities.The comparison of ramets produced clonally can reduce confounding effects from genetic and environmental factors.In the high-density population,48％ of ramets were male without female flowers,but in the low-density population all ramets were monoecious.We observed allometric growth in reproductive allocation with ramet size,as evident in biomass of reproductive structures and number of flowers.However,within both populations female and male flower production were isometric with ramet size,in contrast to an allometric growth in femaleness as predicted by SDS.Phenotypic gender was not related to ramet size in either population.The results indicated that large plants may increase both female and male function even in animal-pollinated plants,pointing towards further studies to test the hypothesis of size-dependent sex allocation using different allocation currencies.