西双版纳地区4种榕树果实的资源分配及其种子萌发特性

为了解榕树果实的资源分配和种子萌发特征,对西双版纳地区的垂叶榕(Ficus benjamina)、高山榕(F.altissima)、聚果榕(F.racemosa)和无柄雅榕(F.concinna)的果实营养、繁殖资源分配,以及种子萌发特性进行了研究。结果表明,4种榕果的营养分配存在差异,榕果重的种类果肉亦多,榕果大者果腔较大,且种子数量较多,但雄花和榕小蜂数量不一定多。榕果分配给雌性功能及雄性功能繁殖的小花比例也不相同,聚果榕在雌性功能上的分配显著大于雄性功能,其它3种榕果则分配于雄性功能的资源比雌性功能的多,但程度不同。此外,4种榕树的种子大小及重量存在显著的种间差异,以至于影响到种子的萌发率及根茎生长,果实最大的聚果榕种子最多,萌发率高,但由于种子最小,其根茎生长缓慢且短;果实适中的垂叶榕和高山榕种子较大,不但萌发率较高,其根茎生长也较快;果实和种子都小的无柄雅榕,种子萌发率低,根茎生长慢。生长在水热环境好的榕树比生长在相对贫瘠环境的榕树,由于极少面临水热光照等限制,更容易进化出较小的种子,萌发能力和速度也相对较差。这说明不同生境中榕树进化出了不同的繁殖分配机制及资源利用策略来适应环境变化。

Fig Resource Allocation and Seed Germination of Four Ficus Species in Xishuangbanna

In order to understand the characters of resource allocation and seed germination of figs, the allocation to vegetation and reproduction in figs, and seed germination of four monoecious Ficus species in Xishuangbanna, such as F. benjamina, F. altissima, F. racemosa and F. concinna were studied. The results showed that the allocation of nutrition resources was significantly different among four Ficus species. The heavier fig had more pulp and larger fruit size, and the fig with larger cavity had more seeds, but the number of male flowers and fig wasps were not always like that. The proportions of flowers that fig allocated to male (fig-pollinating wasps) and female (seeds) function were different. The allocation to female function in F. racemosa was more than that to male function, while those in F. benjamina, F. altissima and F. concinna were just the opposite and had different degrees. Besides, there were significant differences in seed size and weight among four Ficus species so that they influenced on seed germination rate and the growth of roots and stems. Ficus racemosa had the largest fig size and most seeds, its seed germination rate also high, but the growth of root and stem was the slowest because of the small-sized seeds. Both F. benjamina and F. altissima had medium-sized figs and large seeds, so they not only had high seed germination rate, but also the growth of roots and stems was fast. The fig size and seed number of F. concinna were small, so its seed germination rate was the lowest among four Ficus species, and the growth of root and stem was the slowest too. Ficus species living in warm, humid and better environment had smaller-sized seeds and relatively worse germination ability and speed compared to those living in barren environment, because of few limits on water, heat, and sunlight. Therefore, these suggested that different Ficus species in different habitats had already evolved variant mechanisms of reproduction allocation and strategies of resource utilization to adapt their environments.