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关键词： aquaporin   hydraulic conductivity   major intrinsic protein   osmotic flow   water channel   water permeability  

摘要： Over the last decade, considerable advances have occurred in understanding the molecular biology and biophysics of water permeation across plant membranes and tissues. Spurred on by the rapid advances in cloning and functional characterization of a superfamily of major intrinsic proteins, some of which function as aquaporins, the biophysics of transport of water and small non-electrolytes across plant membranes is being re-examined based on the proposed function of these membrane-integral proteins in their native membranes. This review focuses on a number of issues that are central to an understanding of aquaporin function: (1) the need to be able to test for water-channel activity in native membranes;(2) the implications of the observed solute/water selectivity of aquaporins;(3) the putative functional roles of aquaporins at the cell, tissue and organ levels in plants;and (4) information that can be obtained from studies of the abundance, diversity and expression patterns of aquaporins. It is clear that to answer many of the critical questions that remain concerning aquaporin function, combined studies using appropriate molecular and biophysical techniques will be required.

关键词： 薯蓣属   东北   穿龙薯蓣   保护生物学   生物多样性   濒危机制   分析  

摘要： 人们多年的过量采挖和非持续性利用,是导致穿龙薯蓣种群濒危的最主要外部因素.由这个原因而引起的穿龙薯蓣种群骤减,导致了穿龙薯蓣群遗传多样性的下降,进而形成了穿龙薯蓣种群濒危的内部因素.对正面临濒危的穿龙薯蓣种群提出了如下看法:对正处在濒危状态的穿龙薯蓣种群必须及时采取切实可行,并一是行之有效的保护措施,以加强保护力度.不然,长此以住,穿龙薯蓣物种的灭绝将是不可避免的.因而造成的生物多样性损失,将给人类的生活带来诸多不便.

关键词： 香桂   生殖生物学   胚胎发育   樟科  

摘要： 该文应用光学显微镜、部分应用电子显微镜对香桂(Cinnamomum micranthum Hagata)的花芽分化、雌雄蕊的形态发育和胚胎学进行了初步研究.香桂为樟科樟属植物.根据香桂花芽分化进程和分化形态,将其分化阶段划分为:营养生长期、生殖生长锥形成期、花被原基形成期、雄蕊原基形成期、雌蕊原基形成期共5个时期,历时约4个月.香桂的花芽分化在腋芽上进行.具两性花,花序总状、圆锥状.雄蕊与雌蕊发育不同步,雄蕊早熟.花药具4个花粉囊,第一,二轮药内向,第三轮外向.雌蕊由1心皮构成,只有一枚胚珠,为悬挂的倒生胚珠.双层珠被、厚珠心、珠孔由二珠被共同组成.多个雌性孢原细胞起源于珠心表皮下,通常仅一个发育为胚囊,蓼型胚囊.反足细胞3个,短命;极核在受精时融合,初生胚乳核分裂比合子分裂早.双受精属有丝分裂后型.核型胚乳,未发现胚乳吸收器.果皮由外果皮、中果皮和内果皮构成.种皮由外珠被、内珠被形成.4细胞T-形原胚.对樟科植物雌蕊结构与系统学意义进行了讨论.

关键词： Xylem   Lignin   Plants   Cambium   Gene expression   Cell walls   Biosynthesis   Phloem   Plant cells   Transgenic plants  

摘要： (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'***': new Date().getTime(),event:'***'});var f=***(s)[0], j=***(s),dl=l!='dataLayer'?'&l='+l:'';***=true;***= 'https://***/***?id='+i+dl;***(j,f); })(window,document,'script','dataLayer','GTM-N6GDC22');

关键词： jasmonic acid   octadecanoid   fatty acid desaturase   lipoxygenase   allene oxide synthase   allene oxide cyclase   beta oxidation  

摘要： Jasmonic acid, a linolenic acid-derived cyclopentanone, plays regulatory roles in plant development and responses to environmental stresses, such as mechanical wounding or pathogen attack. The action of JA in regulating plant growth and stress responses often requires the elevation of endogenous levels by de novo synthesis. An especially well studied case has been the synthesis of JA in response to wounding. Jasmonates are synthesised through the octadecanoid pathway, in which linolenic acid is converted into JA by a process that is likely to begin in chloroplasts and end in peroxisomes. Conversion of linolenic acid to 12-oxo-phytodienoic acid in chloroplasts is accomplished through a multi-step enzymatic process involving lipoxygenase, allene oxide synthase and allene oxide cyclase. JA synthesis proceeds with the action of a cytoplasmic 12-oxo-phytodienoic acid reductase and three rounds of beta-oxidation that take place in peroxisomes. Most of the enzymes and the corresponding coding genes involved have been isolated and characterised in different plant species. The majority of these genes are transcriptionally activated by wounding and some of them are also activated by JA, allowing feed-back regulation of the biosynthetic pathway. (C) Elsevier, Paris.

关键词： abscisic acid   biosynthesis   carotenoid   phytohormone   plant   regulation  

摘要： The phytohormone abscisic acid (ABA) is involved in seed dormancy and the response to various environmental stresses. Our understanding of the ABA biosynthetic pathway has been increased recently through the use of plant mutants and the cloning of many of the genes encoding for the enzymes involved. C-40 Xanthophylls are precursors of ABA and are now known to be derived from isopentenyl phosphate (IPP) synthesized in plastids via a mevalonate-independent pathway. Enzyme reactions downstream of zeaxanthin have recently been reported to be important for the precise regulation of ABA levels. Zeaxanthin epoxidase (ZEP) catalyses the conversion of zeaxanthin to violaxanthin. Changes in ZEP gene expression appear to regulate ABA biosynthesis in seeds and roots, but not in leaves which might be expected considering the important role of epoxy-carotenoids in photosynthesis and photoprotection. The isomerization of the resulting all-trans-violaxanthin to 9-cis-epoxy-carotenoids awaits elucidation. Although 9-cis-epoxy-carotenoid dioxygenase (NCED), which subsequently cleaves the resulting carotenoids could use the 9-cis isomers of both violaxanthin and neoxanthin as substrates in vitro, the in vivo substrates remain to be determined. NCEDs are apparently encoded by multigene families and identification of the various members is required to determine their relative contribution to the regulation of ABA levels. Studies on those already available indicate that their up-regulation upon water stress is compatible with a key role in the modulation of ABA levels. The genes encoding for the enzymes that convert the cleavage product xanthoxin to ABA are not yet known, although recently cloned aldehyde oxidases may act on ABA-aldehyde. (C) Elsevier, Paris.

关键词： 安徽   黄精属   生物学特性   资源评估   百合科  

摘要： 本文在野外深入调查和园地栽培观察的基础上，研究了安徽黄精属１１种药用植物的产地分布、生境特点、形态特性、生长节律、化学成分等生物学特性，并用群落样方调查和专项访问相结合的方法，对黄精属各种植物资源的蕴藏量进行了评估，提出了深度开发黄精属植物药用。

关键词： 高等植物   营养元素   吸收   膜转运蛋白   编码基因  

摘要： 高等植物对土壤中营养元素的吸收是其一切生命活动过程的基础，尤其在营养元素缺乏的状态下，更与其抗营养饥饿等特性息息相关。兼于土壤中Ｎ、Ｐ、Ｋ元素缺乏的严重性与普遍性，以及Ｎ、Ｐ、Ｋ对高等植物生长和发育的重要性，有关高等植物吸收营养元素的膜转运蛋白编码基因的分子生物学研究已引起有关学者的高度重视。ＮＯ－３／ＮＨ＋４、ＰＯ３－４与Ｋ＋膜转运蛋白均有低亲和力和高亲和力系统（ＬｏｗＡｆｉｎｉｔｙＴｒａｎｓｐｏｒｔｅｒ＆ＨｉｇｈＡｆｉｎｉｔｙＴｒａｎｓｐｏｒｔｅｒ）。对ＰＯ４３－和Ｋ＋而言，低亲和力系统是组成性表达的系统，在正常营养状态下对根系吸收营养起重要作用。而高亲和力系统是受营养缺乏而诱导表达的系统，对于植物的抗逆性、耐营养饥饿至关重要。迄今为止，与之有关的基因的全长ｃＤＮＡ或全基因已在几种植物中被克隆。此外，对基因的表达特性亦有广泛研究。本文简要概述这三大营养元素的膜转运蛋白编码基因的分子生物学研究现状。

关键词： 生物科学   专业建设   高等农业院校   生物学专业   规范研究   毕业论文   分子生物   植物生物学   微生物学   生物化学  

摘要： 我国高等农业院校50年代初从综合性大学分离出来后,设置的生物科学类专业30多年基本上局限在农学门类的作物学、园艺学、农业资源利用、植物保护、畜牧学、兽医学、林学、水产等一级学科,这些农业应用学科大都以生物学基础理论为学科基础。

关键词： 植物   胞系雄性不育   分子生物学   线粒体DNA  

摘要： 植物的胞系雄性不育的机理十分复杂，国内外学者从细胞形态学、组织化学以及生理生化等各方面对败育的机理进行了广泛研究，但败育的机理仍是个难解的谜。从理论上讲，胞质雄性不育系经多代回交转育后同保持系在核基因组成上是一致的，因此雄性不育系和保持系育性的表达差...