Delayed fertilization and pollen-tube growth in pistils of Fagus japonica (Fagaceae)
Delayed fertilization and pollen-tube growth in pistils of Fagus japonica (Fagaceae)
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DOI：
10.3732/ajb.93.12.1748
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发表时间：
2006-12-01
影响因子：
3
通讯作者：
Tobe, Hiroshi
中科院分区：
文献类型：
--
作者：
Sogo, Akiko;Tobe, Hiroshi
与大多数被子植物在授粉后1或2天发生受精相反，在一些植物目中，包括壳斗目，受精延迟4天至1年以上，这引起了关于为什么受精延迟以及在延迟期间花粉管在雌蕊中的位置和方式的问题。为了回答这些问题，我们研究了花粉管生长在日本山毛榉（壳斗科），这是三心皮，有六个胚珠的雌蕊，利用光学，荧光和扫描电子显微镜。胚珠在授粉时未成熟，需要5周才能完全发育。在这5周内，花粉管从柱头到胚囊的生长与胚珠的发育有关，并间歇地分三个阶段进行，有两个生长停止点，珠柄和珠孔附近。在两个生长停止点，花粉管的数量逐渐从多个减少到一个，受精发生在一个胚珠中，显然比雌蕊中的其他胚珠发育早。因此，延迟受精在配子体竞争和选择中起着重要作用，导致非随机受精。间歇性花粉管生长也可能广泛存在于被子植物中，因为它在其他壳斗目和一个不相关的Garryales目中也是已知的。
In contrast to most angiosperms, in which fertilization occurs 1 or 2 days after pollination, in some plant orders, including the Fagales, fertilization is delayed from 4 days to more than 1 year, raising questions regarding why fertilization is delayed and where and how pollen tubes remain in the pistil during the delay. To answer these questions, we investigated pollen-tube growth in pistils of Fagus japonica (Fagaceae), which are tricarpellate and have six ovules, using light, fluorescence, and scanning electron microscopy. The ovules were immature at the time of pollination and required 5 weeks to become fully developed. During this 5 weeks, pollen tubes grew from the stigma to the embryo sac in association with the development of ovules and intermittently in three steps with two growth-cessation sites, i.e., on the funicle and near the micropyle. The number of pollen tubes was gradually reduced from many to one at the two growth-cessation sites, and fertilization occurred in one ovule that apparently developed earlier than the others in the pistil. Thus, delayed fertilization plays an important role in gametophyte competition and selection leading to nonrandom fertilization. Intermittent pollen-tube growth is also likely widespread in angiosperms because it is known in other Fagales and an unrelated order Garryales.