Influence of supplemental ultraviolet-B on indoleacetic acid and calmodulin in the leaves of rice (Oryza sativa L.)

IR68 and Dular rice cultivars were grown under ambient, 13.0 (simulating 20% ozone depletion) and 19.1 (simulating 40% ozone depletion) kJ m^-2 day^-1 of biologically effective ultraviolet-B (UV-B_BE) for 4 weeks. Plant height and leaf area were significantly reduced by supplemental UV-B_BE radiation. Greater reduction in leaf area than of plant height was observed. A decrease in indole-3-acetic acid (IAA) content and increase in peroxidase and IAA oxidase activities of UV-B treated plants in both cultivars were observed compared with ambient control. Calmodulin content also decreased after plants were treated with high supplemental UV-B for two weeks and medium UV-B treatment for four weeks. The results indicated that peroxidase and IAA oxidase activities in rice leaves were stimulated by supplemental UV-B, resulting in the destruction of IAA which in turn may cause inhibition of rice leaf growth. Although the mechanism is unclear, calmodulin is most likely involved in leaf growth.     

Pattern of tree species diversity in riparian forest fragments of different widths (SE Brazil)

Width is an essential element of the spatial configuration of riparian forests and may be fundamental in determining their corridor function. In the present study we tested the effect of forest width on floristic structure (tree species composition and diversity) in 15 fragments of riparian forest in an agricultural fragmented landscape of SE Brazil. All these fragments were chosen in a geomorphological homogeneous river reach under similar soil, topographic and human disturbance conditions in order to minimize the influence of these factors. The forest widths considered ranged from 30 to 650 m. The results showed that total species richness and climax species richness were significantly greater when we consider larger fragments, as has been observed in other studies. Nevertheless, species diversity and evenness were not significantly correlated with forest width. The analysis of species composition showed that the narrowest fragments were characterized by species well adapted to temporary flood conditions, while medium and wide fragments showed a composition typical of drier upland areas. Therefore, the effect of forest width on floristic structure appears to be more strongly linked to the effect of river floods in the case of the fragments studied. The existence in riparian corridors of a drier forest, in general richer and more diversified than the annually flooded forest, seems to favor the maintenance of regional species diversity in fragmented landscapes.     

美味猕猴桃原生质体再生植株细胞遗传学研究 Ⅱ.性别性状变异和小孢子发生及其发育命运

对美味猕猴桃同一雌株叶原生质体再生植株进行了形态学、细胞学以及育性特性的比较研究,确认该体细胞无性系性别性状发生变异。其中60％雄性再生植株退化的雌蕊仍保留不同程度的雌性化特征,但雌性全不育;小孢子则能发育成有功能的雄配子体,但有一定的功能缺陷。再生雌株中P1组群性状特征与母株相似;P2组群花发育畸形,导致雌性不育或育性极差。细胞学研究表明,小孢子母细胞减数分裂时染色体异常行为对小孢子发生的影响不能决定其性别类型;雌株类型小孢子败育过程有受基因调控的细胞学特征。认为雌株和雄株小孢子的发育受控于不同的基因体系,具性别的特异性。再生植株性别性状发生变异可能是性别控制基因或染色体发生结构性变异所致。母株染色体上累积的结构性变异与该遗传基础具易变性密切有关。     

鄂西南后河自然保护区植物区系研究

后河自然保护区共人维管植物１４１６种,尿属５６８属１６０科。其中蕨类、拟蕨类４１种２８属２０科;裸子植物１８种１１属６科;被子植物１３５７种５２９属１３４科。在科、属、种不同水平上对后河自然保护区植物区系特点进行了较深入的统计和分析。结果显示了该区系的丰富性。复杂性。古老、遗、原始性、温带成分的集中性,古特珍稀危植物群落繁荣的特殊性等特点。因此有理由认为后河植物区系对湖北乃至华中植物区系具有典型的     

Agrobacterium-mediated transformation of élite indica and japonica rice cultivars

A rapid, efficient, routine system has been established forAgrobacterium tumefaciens-mediated production of hundreds of fertile transgenic plants from commercially important rice cultivars, including an indica cultivar, Pusa Basmati 1. Calli induced from embryos of mature rice seeds were cocultivated withA. tumefaciens strain LBA4404 carrying the plasmid pTOK233, then exposed to hygromycin selection followed by an efficient regeneration system. Based on the total number of calli co-cultivated, the transformation frequencies of independent transgenic rice plants including cultivars Pusa Basmati 1, E-yi 105, E-wan 5 and Zhong-shu-wan-geng, were 13.5, 13.0, 9.1, and 9.3%, respectively. T1 seeds were harvested within 7–8 mo of initiation of mature embryo cultures. Data from Southern hybridization analysis proved that foreign genes on T-DNA were stably integrated into the rice genome at low copy/site numbers. Mendelian inheritance of the transgenes was confirmed in T1 progeny.     

Vegetation,environmental characteristics and ideas on the maintenance of alvars on the Bruce Peninsula,Canada

Abstract. Despite international recognition that alvar habitats are important reservoirs of biodiversity, they remain little studied in North America. In this paper, the results are reported on an investigation of alvars in the central portion of their known distribution on this continent. 210 plots were distributed among seven sites and were quantitatively sampled for vascular plants, lichens, bryophytes and a suite of environmental variables. Detrended and Canonical Correspondence Analyses and other methods were used to investigate differences among alvars, within alvars and between alvars and adjacent forested habitats. The plant communities and environmental conditions were highly similar among sites in the study region, yet very different from surrounding habitats. There were abrupt changes in vegetation and environmental conditions from alvar to forest, without the presence of transition zones in the vegetation or environmental gradients as the forest was approached. The environmental factors associated with the change from alvar to forest and with variation within alvar habitat were examined. Some alvars in the study were found to contain stunted, slow-growing trees reaching ages of 524 yr. These same sites appear to have remained unburned for several centuries, while other sites likely burned 90 yr ago. The plant communities were very similar between the alvars that lacked a major, biomass-removing disturbance in centuries and alvars that had experienced catastrophic fire relatively recently. Maintenance of the plant communities and open nature of alvars appears site-specific rather than habitat specific.     

陕西植物地理新分布

报道１７种、３变种、１亚种和１变型为陕西植物地理新分布,４属（毛药藤属、白接骨属、马蓝属、赤车属）为陕西植物地理新分布属。     

Production of Bean yellow mosaic virus resistant subterranean clover (Trifolium subterraneum) plants by transformation with the virus coat protein gene

Transgenic lines of subterranean clover were constructed that contained three different Bean yellow mosaic virus (BYMV) coat protein (CP) gene constructs; full-length CP, the core region of the CP, and full-length CP plus the 3′ untranslated region of the viral genome. Transgenic plants containing the full-length and core CP gene constructs showed high and moderate levels of BYMV resistance. Resistance was measured as a lack or amelioration of viral disease symptoms, which was correlated with a reduction in virus levels and yield loss. A range of different resistance phenotypes was observed. They included reduced infection rates, delay and reduction in local lesion development, and delay and reduction in severity of systemic symptom development. Resistance levels were not correlated with transgene mRNA levels and no transgene-encoded protein was detected in any of the transgenic lines. This is the first example of genetically engineered virus resistance in a clover.     

The role of land plants,phosphorus weathering and fire in the rise and regulation of atmospheric oxygen

The evolution of vascular plants and their spread across the land surface, beginning ～420 Ma, progressively increased the rate of weathering of phosphorus from rocks. This phosphorus supply promoted terrestrial and marine productivity and the burial of organic carbon, which has been the major source of O₂ over geological timescales. Hence, it is predicted that the rise of plants led to an increase in the O₂ content of the atmosphere from ～12 vol %, 570–400 Ma to its present level of ～21 vol % by ～340 Ma. Previous modelling studies suggest that O₂ then rose to ～35 vol % ～300 Ma. Such high concentrations are difficult to reconcile with the known persistence of forests, because rising O₂ increases the frequency and intensity of vegetation fires, tending to decrease biomass and cause ecological shifts toward faster regenerating ecosystems. Rising O₂ also directly inhibits C3 photosynthetic carbon assimilation and increases the production of toxic reactive oxygen species in cells. These effects suppress plant‐induced phosphorus weathering and hence organic carbon burial, providing a sensitive negative feedback on O₂. A revised model predicts that this mechanism could have regulated atmospheric O₂ within the range 15–25 vol % for the last 350 million years.     

Early life stage toxicity of extracts from the African fish poison plants Tephrosia vogelii Hook. f. and Asystasia vogeliana Benth. on zebrafish embryos

Embryos of Danio rerio are highly susceptible to extracts of the plants Tephrosia vogelii and Asystasia vogeliana . The concentration of the dried extracts at which 50% of the embryos were affected (EC₅₀) after 24 h exposure were 320 and 572 μg l⁻¹, respectively; corresponding 50% mortality (LC₅₀) values after 48 h exposure were 493 and 869 μg l⁻¹. Results indicate that the use of these ichthyotoxic plants might have a severe impact on the survival of fish larvae in the field.