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作 者 ：Hu Shi-yi

Keywords:Angiosperms, Plastid inheritance, Uniparental maternal plastid inheritance, Bi-parental plasfid inheritance, Uniparental paternal plastid inheritance, Plastid trans mission,

Abstract:The aim of the paper is to review the cytological basis of plasfid inheritance in angiosperms, including the recent results on eletron microscopic studies of the male cell development and the processes of fertilization, and DNA fluor chrome DAPI in conjunction with epifluoreseence microscopy for in situ detection of plastid DNA in the generative and/or sperm cells of the pollen. It is generally accepted that there are three modes of plastid inheritance in angiosperms namely, uniparental maternal, biparental and uniparental partemal plastid inheritance. From all the data attempt is mdc to summarize the cytological basis of the different modes of plasfid inheritance. The uniparental maternal plastid inheritance is dominant in angiosperms. Its cytological events are characterized as the physical exclusion of plastids, the alteration of plastids during male cell development, and the exclusion of male plastids during syngamy. The plastid alteration is mainly caused by the elimination of plasfid DNA in the generative or sperm cells of the pollen. Evidently, in the biparental plastid inheritance the generative and sperm cells contain plasfids and their DNA persistently, which are regularly transmitted into the zygote and in turn into the next generation. But the frequency of biparental plastid inheritance in certain species may be influenced by: ( 1 ) control of nuclear genotype, (2) the role of the plastidome in the process of plastid transmission and possibly in plastid multiplication, and (3) the ratio of plastid number between male and female cells, and the plastid distribution in the zygote. Recently, using RFLP method, uniparental paternal plastid inheritance is demonstrated in Medicago sativa, Daucus and Pharbitis. These results indicated that this mode of plastid inheritance is definitely present in angiosperms. The cytological mechanism is that the plastids, preserving their DNA, in the generative and sperm cells may also be transmitted into the zygote. On the other hand, the female plastids are incapable of genetic transmission. This mechamism is concerned with the fact that the egg is highly vacuolated is which most plastids are positioned in the micmpylar end. Even though the female plastids present in the zygote may become degenerated, or their DNA degraded. In addition the DNA replication rate is higher in the male plastids than that in the female plastids within the zygote. The relationship of the different modes of plastid in heritance is discussed.

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