Change of DNA Content in Male and Female Gametes of Tobacco (<I>Nicotiana tabacum</I>)

Abstract

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 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.