Studys On Seed Developing Physiological Characteristics And Seed Dormancy Mechanism Of Sinojackia Xylocarpa Hu

The seed development of Sinojackia xylocarpa Hu was observed and analyzed to discuss the mechanisms of seed development and dormancy. The results were showed as follows:1. The content of soluble sugar decreased at first then increased during seed developing, but those of soluble protein and crude fat increased at the same time. While the content of starch decreased on the whole. The activities of amylase and protease all increased, and that of ACP gradually decreased, but combined activities of PGI, MDH, G-6-PDH and 6-PGDH all increased at first then decreased. The contents of IAA, ZR and GA3 all gradually decreased, and that of ABA gradually increased. The ratios of ZR/ABA and GA3/ABA decreased a little, and that of IAA/ABA decreased rapidly, which were correspondent with the feature of seed development. The metabolism active theory, the oxidative pathway theory and the hormone regulation theory were all suitable for explaining the development and dormancy mechanisms of Sinojackia xylocarpa Hu seed.2. The cell wall of endosperm was 2.4μm but it would grow to 15.7μm in mature seeds. Meantime, the outer cell wall of radicle appeared 2.5μm keratinization layer and inner cell wall appeared in cellulose thickening. The black granules increased and grew larger in cells, which would seriously hinder the permeability of endosperm.3. The epidermis of external fruit coat was keratinizated, the mid fruit coat was phellem, the seed-sheel was lignified, and the seed coat was deep scarious, which formed thick outer structure to hinder the permeability of seed.4. The germination percentage of bare embryos of mature seed could be 100% on the pledget and MS basic medium separately, but that of full seeds was 0% and 40%, that of seeds with bare radicle was 85% and 90%, that of seeds with bare cotylodens was 80% and 85%, and that of seeds with slitted endosperms was 45% and 75%. The germination percentage of bare embryos of immature seeds collected in July 25 was 100% on the two medium. This results showed that the embryos of Sinojackia xylocarpa Hu seed were not dormant and the causes of seeds dormancy were the permeability and mechanical obstacle.On the basis of this research, The seed dormangcy type of Sinojackia xylocarpa Hu was physical and physiological .