Somatic Embryogenesis In Dendrobium Candidum Wall Ex Lindl. By Different Light

Light is one of the most important environmental factors for plant growth and development.As a physical factor,it has been widely used in plant tissue cultures for morphogenesis,growth control,photomorphogenesis and its reaction mechanism.Results of many researches have shown that the light has a great effect on morphogenesis,organ differentiation and biochemical indicators in plant callus growth.In this study,the embryonic calli was used as the original material,which were induced by protocorm-like bodies(PLBs)of Dendrobium candidum Wall ex Lind.6 kinds of light quality:red No.1,red No.2,green,blue, white and dark were applied in the culture.During somatic embryogenesis, morphogenesis and isozymes of peroxidase(POD),esterase(EST)and cytochrome oxidase(COD)were analyzed.The somatic embryos of Dendrobium candidum were observed in morphology and it was found that different lights could take different extents effects on somatic embryos during 42 days of culture:the Blue＞White＞red No.1＞Red No.2＞Green＞dark;and in each growth period the order of the growth rate of fresh weight per gram was:White＞Blue＞red No.1＞Green＞red No.2＞Dark.The color of somatic embryos in Dendrobium candidum changed from yellow to green.Under white light and green light,the speed of greening was faster than under blue.In this study,through analysis of POD,EST,COD isozyme zymogram,it was found that the light was related with gene expression of the isozymes.And the common isozyme band was found for each kind of the light:POD isozyme with Rf_P1Rf_P2,Rf_P3,Rf_P1and Rf_P2were in each of the eight periods;EST isozyme with Rf_E1,Rf_E2,and both of them were in each of the eight periods;COD isozyme with Rf_C1,Rf_C2,Rf_C3,Rf_C4,Rf_C5,they were in great difference in each period.In addition,we also found 14 specific bands:red No.1 light with three; green light and blue light each with one;white light with three;darkness with six. To combine with the morphological characteristics and the isozyme zymogram characteristics,we could preliminary understand the development process of the somatic embryos in Dendrobium candidum through the indication of isozyme zymogram.