The effect of phosphite on the sexual reproduction of some annual species of the jarrah (Eucalyptus marginata) forest of southwest Western Australia

Phosphite is a cost-effective fungicide used to control the pathogen Phytophthora cinnamomi which is damaging the diverse flora of the southwest of Western Australia. Three annual species of the southwest jarrah (Eucalyptus marginata) forest of Western Australia (Pterocheata paniculata, Podotheca gnaphalioides and Hyalosperma cotula), were studied to determine the effect of the fungicide phosphite on the species’ reproduction. Phosphite at concentrations of 2.5, 5 and 10 g L^–1 reduced pollen fertility of Pt. paniculata when plants were sprayed at the vegetative stage. Pollen fertility of all three species was reduced when plants were sprayed at anthesis with 10 g L^–1 phosphite. Seed germination was reduced by phosphite in Pt. paniculata and H. cotula when plants were sprayed in the vegetative stage. Phosphite when sprayed at anthesis at a concentration of 5 g L^–1 reduced seed germination of H. cotula. Phosphite at concentrations of 5 and 10 g L^–1 killed a proportion of plants from all three species and up to 90% of Po. gnaphalioides plants. The frequent application of phosphite, therefore, may reduce the abundance of annual plants in this ecosystem. Received: 14 December 2000 / Revision accepted: 10 March 2001     

Demographic studies of three indigenous stand-forming plant taxa (Scalesia, Opuntia, and Bursera) in the Galápagos Islands, Ecuador

Mortality and turnover of some of the most characteristic woody plants of Galápagos have been studied during 25 to 32 years on the islands of Santa Cruz, Santa Fe and Pinta. Scalesia pedunculata, S. helleri subsp. helleri and S. baurii subsp. hopkinsii display comparable patterns of high mortality, rapid turnover and relatively short life expectancy, but occur in different habitats and islands in the archipelago. In contrast, Opuntia echios var. gigantea, O. echios var. barringtonensis, O. galapageia var. galapageia, and Bursera graveolens display low mortality (especially of adults), slow turnover and long life expectancies, and occur in similar habitats on different islands. Conditions that favour one taxon may at the same time negatively affect another taxon, and adults, juveniles and seedlings within the taxa may react differently to the same environmental factors. In the humid zone species S. pedunculata, diebacks may be triggered by strong El Niño events, and mass seedling events are associated with El Niños and a subsequent year of drought. In the other taxa investigated, which are arid zone species, the response to strong El Niño events is less pronounced and, in some respects, also different. The differences in mortality, turnover and life expectancy of the species of Scalesia on the one hand and the Opuntia taxa and Bursera on the other, suggest that both humid and arid vegetation types containing species of Scalesia should get higher conservation priority than arid vegetation types without species of Scalesia.     

Impaired expression of the plastidic ferrochelatase by antisense RNA synthesis leads to a necrotic phenotype of transformed tobacco plants

Protoporphyrin IX is the last common intermediate of tetrapyrrole biosynthesis. The chelation of a Mg2+ ion by magnesium chelatase and of a ferrous ion by ferrochelatase directs protoporphyrin IX towards the formation of chlorophyll and heme, respectively. A full length cDNA clone encoding a ferrochelatase was identified from a Nicotiana tabacum cDNA library. The encoded protein consists of 497 amino acid residues with a molecular weight of 55.4 kDa. In vitro import of the protein into chloroplasts and its location in stroma and thylakoids confirm its close relationship to the previously described Arabidopsis thaliana plastid-located ferrochelatase (FeChII). A 1700-bp tobacco FeCh cDNA sequence was expressed in Nicotiana tabacum cv. Samsun NN under the control of the CaMV 35S promoter in antisense orientation allowing investigation into the consequences of selective reduction of the plastidic ferrochelatase activity for protoporphyrin IX channeling in chloroplasts and for interactions between plastidic and mitochondrial heme synthesis. Leaves of several transformants showed a reduced chlorophyll content and, during development, a light intensity-dependent formation of necrotic leaf lesions. In comparison with wild-type plants the total ferrochelatase activity was decreased in transgenic lines leading to an accumulation of photosensitizing protoporphyrin IX. Ferrochelatase activity was reduced only in plastids but not in mitochondria of transgenic plants. By means of the specifically diminished ferrochelatase activity consequences of the selective inhibition of protoheme formation for the intracellular supply of heme can be investigated in the future.     

铅锌尾矿上自然定居植物

在凡口1#铅锌尾矿库内共有10种植物自然定居,这些植物主要生长在尾矿库的边缘区域.植物在尾矿上的生长、分布明显受到表层尾矿某些物理性质如稳定状况、含水量等的影响,尾矿中的营养物质含量与植物的生长高度以及群落盖度有一定的关系.杜虹花(Callicarpa pedunculata)体内的Pb、Zn、Cu和Cd含量大小顺序为叶>根>茎,而盐肤木(Rhuschinensis)和美丽胡枝子(Lespedeza     

低温环境下施氏鲟的人工繁殖研究

施氏鲟天然繁殖水温为16－19℃,在8－14℃水温中进行人工繁殖,获得成功,催产率85％,在低温环境（8－14℃）中催产,效应时间内水温基本稳定或升高是催产成功的关键,而温度高低与催化成功率没有明显关系。在低温环境中,催产的效应时间大幅度延长,卵母细胞游离速度十分缓慢,应多次少量注射激素,催产才能完全成功,催产激素剂量以怀卵量计算效果较佳;卵化积温非常数。神经胚期胚胎在水温低于11时畸形死亡,孵出期胚胎在水温达13℃才能正常破膜,其它时期胚胎在8．5℃水温中能正常发育。     

东北样带上的克隆植物及其重要性与环境的关系

1997年野外调查资料,对中国东北样带克隆植物沿样带的分布,克隆植物在群落中的重要性以及其与环境因子之间的关系进行了研究,结果表明;克隆植物相对种数（C/Pt)和克隆植物相对重要值（IV）随样带上环境梯度变化呈增加的趋势,群落中克隆植物相对种数与土壤全氮含量负相关,与海拔高度正相关,与年平均温度和年降水相关不显著;克隆植物相对重要值与土壤全氮含量负相关,与海拔高度正相关,与年平均温度和年降水相关不显著,研究还发现,群落中克隆植物种数与非克隆植物种数随样带上海拔高度、年平均温度、年降水梯度变化相关性较差,而克隆植物种数与土壤全氮含量负相关不显著,非克隆植物物种数与土壤全氮含量正相关不显著,根茎型、分蘖型及鳞茎球茎型克隆植物在土壤湿度较差的生境中出现频率较高,而匍匐茎型、根茎鳞茎及根茎球茎型克隆植物在土壤湿度较好的生境中出现频率较高。     

浙江淡水维管束植物的区系特点与地理分布

根据15年的调查结果,对浙江省水生维管束植物的区系与地理分布特点进行了研究。已知浙江有水生维管束植物150种,隶属于78属,42科。将78属归纳为11个分布区类型,以世界分布类型所占比例最高,热带分布属总数多于温带分布属,泛热带分布和北温带分布比例非常高。将150种植物归纳为13个分布区类型,温带分布远多于热带分布,以东亚分布类型最为突出,体现了中国－日本植物区系的明显特征,探讨了浙江水生植物的水平地带性和垂直地带性分布规律,其分布不仅与气候带有关,更与水生的生境的分布格局有关。最后,报浙江水生植物濒危种的受威胁状况。     

秦岭田峪河流域种子植物区系研究

田峪河流域是陕西秦岭植物园的核心区,有种子植物128科,605属,1231种（不含种下等级）。区系分析表明,该流域仍以温带成分为主,占总属的70.96%,热带成分占21.13%,地中海与中亚成分占4.41%,中国特有属占3.5%,稀有濒危植物、单种属和少种属、中国特有属及木本植物均占较大比重,说明了历史起源的古老性,地理成分复杂,联系广泛,分布交错,具有明显的温带特征。     

安徽植物区系新增补

报道了安徽植物区系中1属19种8变种和1变型和安徽地理分布新记录,文中引证的标本均存在安徽农业大学森林利用学院树木标本室（AAUF）。     

不同光强下生长的几种亚热带森林树木的Rubisco羧化速率和碳酸酐酶的活性

9月和12月测定了生长于3种不同光强（100％、36％和16％的自然光）下生长的乔木荷树、黧蒴和灌木九节、罗伞盆栽幼苗叶片的Rubisco羧化速率（RCR）、碳酸酐酶（CA）活性和细胞间CO2浓度（Ci)。当生长光强降低时,4种供试植物的RCR和CA活性明显降低。9月时生长在16％自然光下荷树的RCR和CA比100％自然光者分别降低55％和50％,藜蒴则降低20％和35％,耐有的灌木树的降幅较小,仅为33％－38％（RCR）和22％－30％（CA）。12月的RCR和CA的水平较9月时低,翌年1月时自然林不同光强下生长的同类植物的RCA和CA随光强变化也有类似的趋势。RCR和CA活性呈正相关性,且两者与Ci呈弱负相关。推测高光强可能有利于激活Rubisco,促进CA内化的CO2→DlC（可溶性碳）→CO2活性和DlC的传输过程。