Pollen Germination and Tube Growth
Pollen Germination and Tube Growth
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DOI：
10.1007/978-3-642-02301-9_13
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发表时间：
2010
影响因子：
--
通讯作者：
Dongqiao Shi;W. Yang
中科院分区：
文献类型：
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作者：
Dongqiao Shi;W. Yang
在高等植物中，性器官，例如花药和雌蕊，在空间上是分开的，在雌雄同体的植物中在花内或在雌雄同株的植物中在不同的花内。成功的受精需要雌雄器官和配子体在时间和空间上的协调发展。也已经进化出确保花粉在恶劣环境中存活的机制，并将雄配子传递给包围在胚珠内的雌配子体，胚珠又嵌入雌蕊中。此外，雄配子体和雌配子体之间的相互作用确保了受精的成功，并以高效率和可控的方式发生。高等植物中多细胞配子体和管花受精的出现有助于提高有性生殖的效率。在具有三细胞花粉粒的物种中，如拟南芥和水稻，成熟花粉粒由两个小精细胞和一个大营养细胞组成。然而，在烟草、玉米和其他具有双细胞花粉粒的物种中，成熟的花粉粒包含一个大的营养细胞和一个小的生殖细胞，它们将在最后一次有丝分裂之前在花粉管中产生两个精细胞。由营养细胞产生的花粉管将两个精子输送到雌配子体，这种现象称为管花受精（图13.1）。除了花粉粒中的细胞外，还发育了专门的花粉壁，以保护雄配子并满足传播和与雌蕊相互作用的要求。对于雌配子体，它通常由七个细胞组成，即一个卵细胞，两个助细胞，一个中央细胞和三个反足细胞，这些细胞通常在受精前退化（Yang and Sundaresan 2000）。卵与中央细胞和助细胞共同构成一个功能性的雌性生殖单位，完成吸引花粉管、释放和运输精子以及双受精的任务。本章回顾了我们目前对花粉萌发和花粉管生长的理解，重点是拟南芥和其他模式物种。
In higher plants, the sexual organs, e.g. anther and pistil, are separated spatially either within a flower in hermaphrodite plants or in different flowers as in monoecious plants. Successful fertilization requires temporally and spatially coordinated development of male and female organs and gametophytes. Mechanisms have also been evolved to ensure pollen survival in harsh environments and to deliver the male gametes to the female gametophyte enclosed within the ovule, which in turn is embedded in the pistil. Furthermore, crosstalk between the male and female gametophytes ensures the success of fertilization that occurs at high efficiency and in a controlled manner.The advent of multicellular gametophyte and siphonogamy in higher plants is instrumental in improving efficiency of sexual reproduction. In species with tricellular pollen grains, like Arabidopsis and rice, mature pollen grains are composed of two small sperm cells and a large vegetative cell. However, in tobacco, maize and other species with bicellular pollen grains, mature pollen grains contain a large vegetative cell and a small generative cell that will precede the last mitosis to produce two sperm cells in the pollen tube. The pollen tube, a tubular structure that originates from the vegetative cell, will deliver the two sperms to the female gametophyte, a phenomenon called siphonogamy (Fig. 13.1). In addition to the cells in pollen grains, specialized pollen walls have been developed to protect the male gametes and to meet the requirement for dispersal and interaction with the pistil. With respect to the female gametophyte, it is composed typically of seven cells, namely an egg cell, two synergids, a central cell and three antipodal cells that often degenerate before fertilization (Yang and Sundaresan 2000). The egg, together with central cell and synergids, forms a functional female germ unit (FGU) to fulfil the task of pollen tube attraction, sperm release and transportation, and double fertilization. This chapter reviews our current understanding of pollen germination and tube growth, with a focus on Arabidopsis and other model species.