Department of Biology, Faculty of Science, Prince of Songkla University, Hat Yai, Songkhla, Thailand 90122.
Am J Bot. 2010 Jan;97(1):136-43. doi: 10.3732/ajb.0900100. Epub 2009 Dec 18.
The study of plant responses to touch, particularly the responses of leaves, stems, and roots, has a long history. By contrast, floral responses are relatively unexplored. Stigma closure is common in the Bignoniaceae, but the factors influencing it are not well understood. We investigated factors influencing stigma closure and reopening and its effects on pollen receipt in seven Oroxylum indicum trees near Hat Yai, Thailand. The effects of pressure, conspecific and heterospecific pollen, and pollen load (the amount of pollen deposited) on stigma behavior were examined in 270 flowers (of the total 430 flowers evaluated in the entire study). Pressure alone resulted in faster closure than did conspecific pollination and faster reopening than did heterospecific pollination. Stigmas never reopened after conspecific pollination. Pollen load had no effect on stigma behavior. Stigmas discriminated between conspecific and foreign pollen; they reopened only after pollination with the latter. A manipulative experiment revealed that stigma closure did not affect the number of conspecific pollen grains received. We also counted pollen tubes in styles that were either hand-supplemented with outcross conspecific pollen or open-pollinated. Pollen tube numbers were highest after light pollination (∼900 grains), indicating that interference among pollen grains may occur after pollination with very heavy loads (>6000 grains). Possible fitness consequences of these responses are discussed.
植物对触摸的反应，尤其是叶子、茎和根的反应，已有很长的研究历史。相比之下，花的反应则相对较少被探索。柱头闭合在紫葳科中很常见，但影响它的因素还不是很清楚。我们研究了影响柱头闭合和重新开放及其对花粉接收的因素，在泰国合艾附近的 7 棵黄蝉树上进行了调查。在 270 朵花（整个研究中评估的 430 朵花的总数）中，考察了压力、同种和异种花粉以及花粉负荷（花粉沉积量）对柱头行为的影响。单独的压力导致柱头比同种花粉授粉时更快地闭合，比异种花粉授粉时更快地重新开放。同种花粉授粉后，柱头从未重新开放。花粉负荷对柱头行为没有影响。柱头在同种和异种花粉之间有区别；只有后者授粉后才会重新开放。一个操纵实验表明，柱头闭合不会影响同种花粉粒的数量。我们还计数了经过人工授粉的花柱中的花粉管，这些花柱要么是用异交同种花粉补充的，要么是自然授粉的。轻授粉后花粉管数量最高（约 900 粒），表明在授粉时花粉负荷非常大（超过 6000 粒）后，花粉粒之间可能会发生干扰。讨论了这些反应的可能适应后果。
