位置效应对喉毛花(龙胆科)的花特征和繁殖成功的影响

Effects of the Position on Floral Traits and Reproductive Success of Comastoma pulmonarium(Gentianaceae)

同一个植株上不同位置花的特征和繁殖成功通常表现出较大的差异,这种差异是源于不同位置花间的资源竞争还是植株本身发育过程中的结构效应仍需进一步阐明。作者以青藏高原高寒草甸中常见的一年生自交植物——喉毛花(Comastoma pulmonarium)为研究对象,通过控制植株的资源状态比较植株上不同位置花的特征和繁殖成功,探讨花序内资源竞争和结构效应的影响。结果发现,与其它位置的花相比,位于植株顶端的首先开放的花具有较大花高度和花直径,并产生了更多的花粉和胚珠;但蕾期去除顶花后,其它位置的花高度和花直径与对照植株上同位置的花相比并没有显著变化,表明喉毛花不同位置的花特征变异是由植株发育过程中的结构效应引起,改变植株的资源状态不会改变喉毛花的花特征。喉毛花顶果的种子数量、重量和萌发率均高于其它位置果实的种子;但去除顶花后,其它位置果实的种子数量与对照植株相同位置的果实相比,均呈现增加的趋势,表明喉毛花顶果以外其它不同位置果实的种子发育期间存在资源限制;改变植株的资源状态后,植株的可用资源会在不同位置的果实间重新分配,这对后期发育的果实具有一定的保障作用。研究结果表明,喉毛花植株上不同位置间的花特征和繁殖成功差异分别由结构效应和资源竞争引起,与其它的研究结果存在分歧,其原因可能与喉毛花一年生的生活史特征和资源有限的高原环境有关,但仍需要进一步的研究证明。

Variations in flower traits and reproductive success among differently positioned flowers within one plant might result from resource competition and/or architecture effect, but this argument needs to be further demonstrated in more species. We studied the flower traits and reproductive success of flowers from different positions in Comastoma pulmonarium （Genetianaceae） , an alpine selfing annual herb of the Qinghai-Tibet Plateau. Our results showed that the flower diameter, flower height, number of pollen grains and ovules from the top flower, were all much more than those from flowers positioned lower within the inflorescence. After removing the top flower buds, we found no significant changes in either flower diameter or flower height in the remained flowers compared with the same positioned flowers on control plants, indicating architectural effect on flower traits. Meanwhile, seed number, seed weight and seed germination rate in the top fruits were higher than those in other positioned fruits. Given the removal of the top flower buds, furthermore, seed number of other positioned fruits increased compared with those fruits in the same positions on control plants, suggesting resource competition and resource reallocation happened among the developing fruits when the available resources within a plant was changed. This mechanism could, to some extent, assure reproductive success of the late-developed fruits. Our results showed architectural effect on flower traits and resource competition during the development of fruits in C. pulmonarium, which was quite different from some previous reports. We speculated the short life history （annual） and the alpine environments of the Qinghai-Tibet Plateau （resource limitation） could be the main factors to explain this phenomenon.