Physiological Study On Sex Differentiation Of Flower In Cucumber

I~: ft~~Jf~ -5- Physiological study on sex differentiation of flower in cucumber (Cucurnis sativus L.) ABSTRACT The physiological, biochemical and cytological changes of the plants were studied during the floral sex organ development using the full female line (ZQ- 18) and the strong male line (ZH-20) of cucumber that were purified for more than 10 generations to be homogenous, and discussed the mechanisms of floral sex differentiation and development. In this paper, we established a new d~醤g method for the pressing pollens, which made cucumber pollens more clear-cut, and used paraffin wax section to study the development of female and male flower of cucumber. The developmental process of male and female flower of cucumber at cell level was observed by means of the methods above, and compared the changes of endogenous plant hormones, polyamine, nucleic acid and protein content at several distinct developmental stage (hermaphrodite, microspore mother cell, microspore tetrad, early single pollen grain and mature male flower and hermaphrodite, megaspore mother cell, megaspore tetrad, megaspore and mature female flower, respectively ) . The results were showed as follows. The developmental process of both flower, male and female, was different. Male flower developed slightly faster than female. The endogenous plant hormones, polyamine, nucleic acid and protein were all involved in the differentiation and development of the sex organ of cucumber. Both GA3 and IAA content of female flower was higher than that of male flower at metaphase and anaphase. IAA content increased continuously from megaspore mother cell stage until the maturation of mail flowers. It seems likely that IAA is a key hormone for sex organ -6- development of cucumber. Whereas ZT is favourable to development of megaspore mother cell and ABA is favourable to development of megaspore and microspore tetrad. The high ZT(IAA ratio was related to producing megaspore mother cell and pollen grain. It appears however that the formation of megaspore tetrad associated with the high GA3/ZT ratio. PAs, Spin and Cad might relate to the fate of the hermaphroditic flower, directing to megaspore or to microspore. The increase of PAs, 5pm and Cad resulted in the development into female flower from hermaphroditic flower. On the contrary, the decrease of PAs, 5pm and Cad induced the development of male flower. Put played a important role in the development of microspore tetrad and pollen grain. The rise of Cad was related to the development of microspore and megaspore tetrad. 5pm was related to the maturation of the pollen grain. Cad, Spd and Spin associated with the development of megaspore mother cell, and Cad was related to the development of megaspore tetrad. DNA content significantly increased at the early stage from hermaphrodite to unisexual process. Protein contents in female and male flower were concordant strongly with RNA content. Protein and RNA content in the male, however, increased quickly after microspore mother cell stage and they increased quickly after megaspore tetrad in the female.