种子植物的选择性败育及其进化生态意义

种子植物的选择性败育是指植株在花粉源、传粉次序、果实在植株上的位置和发育果实中的种子数目等因素或者这些因素综合作用的基础上对发育中的幼果或种子选择性败育的现象。植株可以选择性地败育位于果序顶部或基部的果实以及位于果实基部、中部或柱头端的种子。此现象在被子植物中比较普遍,特别是在豆科、十字花科和紫草科中最为常见。导致植物选择性败育的主要原因主要有资源限制和遗传因子两个方面。植物通过选择性败育部分自交或基因型较差的果实或种子,不仅可以提高母本和后代的适合度,而且还可以提高果实或种子的扩散效率。因此,对选择性败育的研究在深入了解植物的结实结籽格局、探讨其进化式样与机制等方面具有重要意义。该文系统总结了国际上有关植物选择性败育的研究工作,重点介绍了选择性败育发生的式样、导致选择性败育的因素、选择性败育的进化生态意义,以及目前研究选择性败育现象的主要方法,并对该领域今后研究前景进行了展望。

SELECTIVE ABORTION AND ITS EVOLUTIONARY, ECOLOGICAL SIGNIFICANCE IN SEED PLANTS

Selective abortion in seed plants means selective abortion of developing fruits/seeds based on pollen source,order of pollination,location of fruits on plant,number of developing seeds,or some combination of these.In species with linearly arranged ovules,such as occurs in members of Fabaceae,embryos at the peduncular,stigmatic,or both ends of the fruit can be selectively aborted.Position of fruit within the inflorescence also has a marked effect on abortion.Selective abortion has been documented in many species of Fabaceae,Brassicaceae and Boraginaceae.The primary factor causing selective abortion of fruit and/or seeds is resource limitation.Competition for limited maternal resources occurs among fruits and seeds.Thus,those that are initiated first and have the faster rate of growth can capture more maternal resources and thus are less likely to be aborted than those that are initiated later.Genetically correlated factors also can result in selective abortion.In some species,fruits from cross-pollinated flowers tend to have more seeds that are more likely to mature than fruits from self-pollinated flowers.Methods used to investigate selective abortion include 1)removing a fraction of the ovules at an early stage,2)hand-thinning some young fruits or flowers,and 3)using molecule techniques of RAPD and isoenzyme analyses.Selective abortion can increase offspring quality.Progenies that are selectively matured have higher vigor,germinate to higher percentages,produce more leaves,inflorescences and flowers,and mature more seeds than those that are randomly matured.Aborting some seeds also can reduce wing load(ratio of fruit weight to fruit surface area),improve dispersal distance,and decrease sibling rivalry.Thus,selectively aborting some selfed and/or inferior genotype fruits/seeds increases the fitness of the maternal plant,its offspring,or both.Therefore,research on selective abortion is important to understanding patterns of fruit-set and/or seed-set and its evolutionary pattern and mechanism in angiosperms.We review recent advances in selective abortion research in angiosperms,with emphasis on 1)patterns of selective abortion;2)factors affecting selective abortion;3)evolutionary,ecological significance of selective abortion;and 4)primary methods used to investigate selective abortion.We also discuss prospects for further research.