烟草雌、雄配子DNA含量变化

Change of DNA Content in Male and Female Gametes of Tobacco(Nicotiana tabacum)

:采用显微分光光度法测定了烟草(Nicotiana tabacum)精细胞和卵细胞的DNA含量。烟草是二胞花粉,花粉萌发后生殖细胞在花粉管中分裂形成精细胞。授粉后45h花粉管到达子房,在花粉管内的精细胞DNA含量为1C。当花粉管在退化助细胞中破裂,释放出的两个精细胞开始合成DNA。在与卵细胞融合前,两个精细胞DNA含量接近2C。随着精细胞的到达及合成DNA,卵细胞也开始合成DNA,融合前的卵细胞DNA含量也接近2C。精、卵细胞融合后,合子DNA含量为4C。烟草雌、雄配子是在细胞周期的G2期发生融合,属于G2型。

The nuclear DNA content of male and female gametes of tobacco （ Nicotiana tabacum ） was measured using DAPI stain and micmspectrofluorimetrie measurement. Tobacco pollen is bicellular at anthesis, containing a vegetative cell and a generative cell, which divides to form two sperm cells in a pollen tube. The nuclear DNA content of generative cell in a pollen tube was at 2C level and that of two sperm cells in a pollen tube, which elongated in the style, at 1C level. Two sperm cells began to synthesize DNA after both were released in the degenerated synergid, and the quantity of nuclear DNA in both sperm cells approached 2C level before both fusing with egg and central cells. During this process, the nuclear DNA content of egg cell also began to increase and approached 2C level before fusing with sperm cell. After male and female gamete fused, the nuclear DNA content of zygote reached 4C level. Therefore, the fusion of male and female gametes of tobacco was at G2 of cell cycle, and this fusion of fertilization belonged to G2 type. This result displayed the fertilization multiformity in angiosperms.