The reproductive strategy in a Chloris virgata population in response to precipitation regimes

Resource availability influences plant growth and reproduction. Here, a controlled experiment was conducted in order to evaluate the adaptation response of Chloris virgata to different precipitation conditions, and to further predict the reproductive strategy in a population of C. virgata under different precipitation regimes. Three regimes (low, typical and high) of water addition were used to simulate current precipitation patterns. Total 20 individuals for each treatment were analyzed to compare tiller number, spike traits, seed traits, the relationship between seed size and seed number, and so on. In addition, the effects of different precipitation regimes on offspring vigour of C. virgata were also studied. Results indicated that tiller number, spike number, seed yield and seed number were unchanged under different water addition regimes. While seed size was about 0.5 mg at typical and high precipitation levels and were higher than that in low precipitation level. The higher seed mass per spike and spike mass both occurred at typical and high precipitation levels. Significant positive correlations between seed mass and non-seed mass in C. virgata in response to precipitation regimes were largely allometric (size dependent), as was a significant negative correlation between seed size and seed number at low precipitation. The highest germination rate and seedling weights both occurred at typical and high precipitation levels. These findings showed that different precipitation regimes affected reproductive strategy of C. virgata. C. virgata will not benefit from low precipitation, while typical and high precipitation will improve seed traits and offspring vigour of this species.

资源可获得性会影响植物的生长与繁殖。本研究开展一项受控实验，旨在评估虎尾草（Chloris virgata）对不同降水条件的适应响应，并进一步预测该物种种群在不同降水格局下的繁殖策略。实验设置低、常规、高三种补水梯度，以模拟当前降水格局。每个处理组共计20个个体，通过分析其分蘖数、穗部性状、种子性状以及种子大小与种子数量间的关联等指标开展组间比较。此外，本研究还探究了不同降水格局对虎尾草后代活力的影响。
结果显示，不同补水梯度下，虎尾草的分蘖数、穗数、种子产量及种子数量均无显著变化。而常规与高降水水平下的种子大小约为0.5mg，显著高于低降水水平。单穗种子质量与穗部生物量均在常规与高降水水平下达到更高水平。虎尾草响应降水格局时，种子质量与非种子质量间的显著正相关大多属于异速生长（即依赖于个体大小），低降水水平下种子大小与种子数量间的显著负相关关系亦是如此。最高发芽率与幼苗生物量均出现在常规与高降水水平下。
上述研究结果表明，不同降水格局会影响虎尾草的繁殖策略。低降水条件无法为虎尾草带来益处，而常规与高降水水平则可优化该物种的种子性状与后代活力。