青藏高原东缘块茎堇菜鳞茎分配的个体大小依赖性

Size-dependent of Qinghai-Tibetan Plateau Viola tuberifera(Violaceae)bulbs allocation

关键词:  繁殖生态学, 生长期, 混合交配, 无性繁殖, 总生物量

Key words:  reproductive ecology, life-history, mixed-mating, asexual reproduction, total biomass

摘要:

块茎堇菜(Viola tuberifera)为青藏高原特有两型闭锁花植物,属多年生草本,具独特的混和交配系统,既可通过早春开放花异花受精和夏季地上地下闭锁花自花受精有性繁殖,还可通过秋季新鳞茎无性繁殖产生后代。高山环境下,异花受精常因花粉限制而无法正常进行,自花受精和克隆繁殖成为保障植物种群正常繁衍的不二之选,而克隆繁殖更能在植株资源消耗最小的情况下保障子代的存活。该文以青藏高原东缘高寒草甸的混合繁育植物块茎堇菜为研究对象,探索其生长期内鳞茎分配的个体大小依赖性,以及植株如何权衡鳞茎的资源分配以适应个体大小的变化。结果表明:块茎堇菜生活史阶段的鳞茎分配具有个体大小依赖性,鳞茎分配与个体大小呈极显著负幂指数相关关系(P<0.01),个体越大,鳞茎分配越小; 反之,个体越小,鳞茎分配越高。即块茎堇菜对鳞茎的资源投入受个体大小的制约,通过鳞茎分配比例的高低响应植株自身资源状况的变化,保障在高寒环境下植物种群的生存和繁衍。该研究结果为高山植物克隆繁殖的生活史进化提供了依据。

Abstract:

Viola tuberifera is a typical dimorphic cleistogamous plant which endemic to Qinghai-Tibetan Plateau and its eastern neighbour region, belongs to perennial herb, possessing mixed-mating reproductive system, which conducts not only sexual propagation via both open, aerial chasmogamous(CH)flowers in spring and closed, obligate self-pollinating aerial and subterranean cleistogamous(CL)flowers in summer, but also asexual reproduction via new bulbs in autumn reproducing offsprings through winter. Chasmogamous flowers depend on pollinator, such as bumblebees, obligate cross-fertilization producting bigger and few seeds. Cleistogamous flowers do not need pollinators, they can pollinate by themselves and produce smaller and abundant seeds. Further to say, survival ratio of chasmogamous flowers seedings is lower than the cleistogamous flowers offprings. In particular, while plant under harsh environment, cleistogamy can provide reproductive assurance and cost economically. Three flowers are all sexual propagation. Only vegetative organ-bulbs via asexual propagation. Bulbs prapagation can also assure reproduction under adverse habitat. Especially in alpine ecosystem, plants always face to pollination limatation, at this time vegetative propagation can produce offsprings which are similar to stock plant and form ramets to fight for habitats and resources. Parents and offsprings together resist stern climate and through cold environment. That is to say, bulbs reproduction can ensure V. tuberifera surivial and continuation in the high alpine environment and cost mininum resources to through winter. Sexual reproduction is conducted before asexual reproduction and two opposite reproductive strategies can ensure survival together in the whole life history. In the alpine district, allogamy always face pollen limitation and cannot assure plants reproduction, whereas autogamy and clonal reproduction are alternative choices to ensure propagation of plants populations, as well as clonal reproduction can furtherly assure offsprings' survival with the lowest resources assumption. In this paper, mixed-mating plant-V. tuberifera in eastern Qinghai-Tibetan Plateau alpine meadow were chosen as study material, probing into size-dependent on bulbs allocation during life-history, aiming at how V. tuberifera could trade off resource allocation on bulbs to adapt to changes of individual size, providing evidence for life-history evolution of clonal reproduction in alpine plants. The results showed that bulbs allocation of V. tuberifera endemic to eastern Qinghai-Tibetan Plateau existed size-dependent in the whole life history, bulbs allocation and individual size showed extremely significantly negative exponent correlationship(P<0.01). The bigger the individual size was, the lower the bulbs allocation was, and vice versa. Although individual size was small, plants allocate amounts of resources to asexual organ—bulbs, assuring propagation in winter and survive themselves. When the bulbs allocation came to the maximum, though individual size became bigger, proportion of bulbs did not change any more. Therefore, that individual size controlled resource allocation was within a definite range. Beyond the certain range, individual size no longer affected bulbs allocation. That is to say, resource allocation on bulbs in V. tuberifera is controlled by individual size in a certain range, plants via altering proportion of bulbs allocation to adapting to inner resource condition changes of V. tuberifera, ensuring plants population survival and offsprings propagation in the alpine environments.