抗旱作物上岗记

一边是水资源的严重短缺，一边是干旱导致的农业减产，无疑使世界粮食危机雪上加霜。水资源正成为世界多数国家制约农业发展的重要因素，培育“不怕渴”农作物品种成为摆在世界育种学家面前的共同难题，也是节水农业中最有效的技术手段。     

刀豆球蛋白A对Ehrlich腹水癌细胞的膜电位和表面电荷的影响

本文报告用荧光探剂diS-C_3—(5)和细胞电泳技术研究刀豆球蛋白A(ConA)作用于Ehrlich腹水癌细胞引起的膜电位和表面电荷的变化.ConA与细胞膜相应受体结合,导致在膜上的diS-C_3-(5)的荧光强度增加,表明细胞去极化.经用缬氨霉素诱导的钾扩散电位校正,与光学讯号变化相应的膜电位变化约是20mv.细胞经G毒毛旋化苷处理后,ConA引起的去极化程度比未处理过的细胞大.ConA作用于Ehrlich腹水癌细胞使细胞电泳迁移率变小.表明细胞表面负电荷数目减少.本文对这些变化的可能机制和相互关系进行了讨论.     

Mitosis and microtubule organizational changes in rice root-tip cells

The pattern of change of the microtubule cytoskeleton of the root-tip cells of rice during mitosis was studied using immunofluorescence technic and confocal laser scanning microscopy. All the major stages of ceil division including preprophase, prophase, metaphase, anaphase and telophase were observed. The most significant finding was that in the preprophase cells microtubules radiating from the nuclear surface to the cortex were frequently seen. During development these microtubules became closely associated with the preprophase band and prophase spindie indicating that the microtubules radiating from the nuclear surface, the preprophase band and the prophazc spindle were structurally and functionally closely related to each other. Granule-like anchorage sites for the radiating microtubules at the muclear surface were often seen and the possibility that these gramle-like anchorage sites might represent the microtubule organizing centres was discussed.     

A Technique to Analyse Succession Data from Permanent Plots

IIntroductionSuccessionstudyIsaspeclalfleldInvegetationecology（Greig—Smith1983）．ItreferstocummulatlvechangeInvegetationovertime．Florl幻IcgradientsIndicativeofsuccessionaltrendsmayemergefromconventionalordinationIfextrinsic！nformatlonallowsthemtobel－dentlfledassuch．Inthespedalcaseofforestvegetation,forInstance,Informationonthesize—classesoftreespedespresentmaypermitsuccessionalgradientslobeldentlfleddirectly（Goff1968,Carleton＆Maycock1978）．Fewauthors,however,haveattempted…     

Changes of intracellular Na+ concentration in erythrocytes caused by pulsed electrical field

Changes of sodium ionic concentration of human erythrocytes applied to pulsed electrical field (PEF) were studied by using shift reagent and NMR spectroscopy. The results show that the concentration of intracellular Na⁺ increases with the increasing intensity of PEF when the erythrocytes are applied to PEF with higher intensities. The relationship between intracellular Na concentrations and the intensities of PEF does not follow linear or exponen-tial behavior. As the intensities increase, the intracellular Na⁺concentrations increase even faster by an exponential curve. However under effects of PEF at lower intensities, intracellular Na⁺ concentration decreases. Ouabain can in-hibit the decrease of intracellular Na concentration, and the inhibition increases with the increasing concentration of ouabain, suggesting that Na⁺ , K⁺ -ATPase on cell membrane can be activated by PEF at lower intensities. Direct measurement of activities of the enzyme by using Malachite green method has confirmed this observation. Cell perme-abilities to ions, activation of enzymes by electrical fields and transmission of physical signals like PEF across cell mem-branes are discussed.     

干旱和湿润生境下辽东栎群体遗传结构及其适应意义的初步研究

应用同工酶分析方法,测定北京市东灵山区两个分别代表干旱和湿润生境的辽东栋（ＱｕｅｒｃｕｓｌｉａｏｔｕｎｇｅｎｓｉｓＫｏｉｚ．）群体的遗传结构。共分析统计了１３ 个酶系统３０ 个位点。结果表明：辽东栎群体内部存在丰富的遗传变异（多态位点百分率为８６．６％ ,等位基因平均数为２．２５）。两群体遗传结构的相似性程度很高（Ｄ＝ ０．０２９, ＧＳＴ＝ ０．０４８）;但在个别位点上仍存在较大差异,这些差异的产生可能与对小生境的适应有关。对不同年龄段的初步分析结果显示,基因频率的动态变化可能有其适应意义     

美丽的草原，我的家

“敕勒川,阴山下,天似穹庐,笼盖四野。天苍苍,野茫茫,风吹草低见牛羊”。内蒙古自治区从东到西跨度达4000千米,自然条件复杂,生物种类丰富,植物群落和植被类型繁多。呈现森林、森林草原、典型草原、荒漠草原、荒漠、湿地等多种     

神奇的营养素

研究表明,人体需要大约40种维生素和矿物质。虽然人们吃下去丰富的食物,但获得的某些至关重要的维生素和矿物质却仍然太少。究竟什么样的合理饮食才能使人们生活得更好呢?     

沉浸雨林

作为中国科学院西双版纳热带植物园的研究生,第一年要到位于北京的研究生院完成理论学习。虽然是理论学习,但已经不再是看书、听课、考试的程式化生活了,除了课程,还要大量阅读国内外的专业文献,为学位论文的选题和论证做好准备。在堆积如山的文献面前,曾经认为很有新意的选题却早有研究报道了,要凝练     

群翔于花丛中的红衫小老虎

<正>英气逼人的红衫小老虎2006年五一的前几天,我在成都文殊院第一次看到了红头长尾山雀,一群,大约二十几只。红头长尾山雀一边觅食一边"吱吱吱"鸣叫——像银喉长尾山雀以及其他长尾山雀的尖细叫声。