Study on Seed Dormancy Mechanism and Breaking Technique of Gynostemma pentaphyllum(Thunb.)Makino

Germination characteristics,dormancy causes,dormancy types and methods of breaking dormancy of Gynostemma pentaphyllumseeds which were collected from Jinxiu county in Guangxi,were investigated in this paper,so as to provide scientific basis for the seed propagation of G.pentaphyllum.The results indicated that:(1)The viability of G.pentaphyllumfreshly mature seeds was 91%,but when incubated at 10 ℃~35℃constant temperature and 15℃/25℃alternating temperature,germination percentages of them were less than 10%.The viability of freshly seed was significantly greater than the germination percentage,which indicated that there was obvious dormancy phenomenon in freshly collected G.pentaphyllumseeds.(2)G.pentaphyllumseed coat is water permeable,the embryo fully developed,the germination percentage of in vitro embryos was(78.0±4.8)%,and in vitro embryos could produce normal seedlings,which indicated that in vitro embryos of G.pentaphyllumseeds were non-dormant.(3)Water extract of whole seeds and crushed seeds had inhibitory activity on seed germination rate,height of seedling and root length of seedling of cabbage.The inhibitory effect enhanced significantly with the increase of water extract concentration,and the inhibitory effect of crushed seeds was greater than that of whole seeds;When water extract of crushed seeds at a concentration of 5%,seed germination rate,height of seedling and root length of seedling of cabbage were only 18.0%,0.1cm and 0.1cm respectively,77.1%,97.3% and 95.8%lower than that of control.These indicated that there were water-soluble germination inhibitory substances in seed coat and endosperm of G.pentaphyllum,which was one of the main causes of seed dormancy.(4)GA3 and 6-BA could not improve the germination of G.pentaphyllumseeds,but cold stratification could promote seed dormancy release.These results indicate that G.pentaphyllumseeds possess non-deep physiological dormancy.(5)Low-temperature dry storage was the best way for seed conservation of G.pentaphyllum,which could also break seed dormancy.