烟草雌、雄配子DNA 含量变化

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45 h 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。

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

The nuclear DNA content of male and female gametes of tobacco ( Nicotiana tabacum) was measured using DAPI stain and microspectrofluorimetric 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 DNAin 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 .