种子休眠与破眠机理研究进展

种子休眠机理主要围绕透性、抑制剂作用和光敏素转化等方面的研究而建立。种皮的阻碍作用可能是由于种皮的物理或化学特性引起．可导致对水、光、气体或溶质的透性改变。抑制剂作用机理是抑制物质可抵消促进细胞分裂和生长发育的激素的作用。光敏素转化机理来源于与休眠有关的生物活性化学物质的合成、活化或破坏受光诱导的观点，由于发现了光敏素蓝色蛋白的活化型（Pfr）和钝化型（Pr）而得到强有力的支持，种子光休眠取决于光敏素蓝色蛋白的活化型（Pfr）含量和Pfr／（Pr＋Pfr）比值。目前，打破休眠的方法一般有机械破皮法、激素处理法、分子生物学技术法、物理处理法（如激光、烟、热等处理技术）、CO2处理法等。激素的平衡由抑制剂占优势向促进物占优势的变化是打破休眠的决定因素。研究破眠机理的分子生物学技术有多种，包括ABA突变体的利用、分子标记、转基因技术、用反义RAN阻止基因的表达、cDNA克隆技术等。用激光照射种子，把适宜的光射入细胞，可增加细胞生物能，促进种子发育，从而可能打破休眠。热处理的机理是由于加热可以增加种皮的透气性。CO2之所以能提高某些物种的萌发率，在于其影响了种子内部乙烯的敏感性。

Progresses in Seed Dormancy and Dormancy-Breaking Mechanisms

Seed dormancy mechanisms mainly focus on seed permeability,inhibitor action and photofrin transformation.Testa inhibition probably results from physical or chemical properties of testa,and can lead to the penetrability changes of water,light,air and solutes.The mechanisms of inhibitor action are that inhibiting substances can counteract the actions of the hormones capable of helping cell division and development.The mechanisms of photofrin transformation were originally based on the viewpoint that the synthesis,activation or breakdown of dormancy-related bioactive substances are induced by light and this has gotten strong support because the discoveries of active and passive types(Pfr and Pr) of photofrin blue proteins,and the dependence of seed dormancy on Pfr content and Pfr/(Pfr+Pr) ratio.Currently,the commonly-adopted dormancy-breaking methods are mechanically breaking testa,treating seeds with hormones,molecular biological techniques,physical techniques(such as laser,smoke curing,and heating),and carbon dioxide.The hormone balance that swings from the dominance of inhibiting substances to the dominance of growth-assisting substances is the major dormancy-breaking factor.There are quite a few molecular biological techniques of studying the dormancy-breaking mechanisms,which include ABA mutant use,molecular markers,transgenic technique,gene-expression blocking by antisense RNA,and cDNA cloning.Seeds are exposed to laser and receive a certain amount of radiation,which can increases the biological energy of their cells thus enhancing their development and breaking their dormancy.The mechanism of heating treatment is that heating can increase the air permeability of testa.The reason for carbon dioxide to raise the germination rates of some species is that it affects ethene sensitivity in seeds.