Study On The Crucial Techniques Of Cymbidium Grandiflorium In Tissue Culture

In this article, several crucial technical questions have been studied with meristem or pseudo bulb as explants, including the best culture medium, multiplication of protocorm like-body(PLB),mechanism of browning, and method of browning prevention. The problem of browning was emphasis. The rapid propagation system targeting to provide technical reference for the mass production of cymbidium grandiflorium has been set up. The study on the browning mechanism laid a foundation for the settlement of the common problem in woody plant culture.The main results of research in this thesis are followed:1. The results of the best culture medium were reported as follow:â‘  The inducement medium of PLB: MS+BA1.5mg/l+NAA0.1 mg/l, the induction rate could be 81.4% after 2 months.â‘¡ The multiplication of PLB: MS+BA1.0mg/l+NAA0.03mg/l, the quantity of multiplication could be 5.8.â‘¢ The differentiation of PLB: MS + BA0.5mg/l + NAA0.8mg/l,the differentiation rate could be 89.4% after one month.â‘£ The medium of rooting: 1/2MS + BA0.3mg/l + NAA0.5mg/l+banana mud 150g/l,the roots are strong.2. The culture condition as follows was found to be suitable for multiplication of PLB: liquid vibration culture, thin cross section (TCS) culture and 5 protocorm like-body of section size(see from Figure 3.1 to Figure 3.3).3. The comparison of total phenols (TP), BD(browning degree), polyphenoloxidase (PPO) and phenylalanine ammonia-lyase (PAL) activity between the controlled and heat shock group showed that the index values of the later were lower than those of controlled(see from Figure 4.1 to Figure 4.3). The mechanism of wound-induced browning may be supposed that PAL firstly converts phenylalanine to mono- and diphenols derivatives, then the derivatives react with PPO, which results in browning. While when heat shock was impressed on the explants, heat shock proteins (HSPs) was produced instead of PAL. The total phenols reduced accordingly. And there are less substrates (phenols) that can react with PPO and other unknown substances so as to prevent explants browning efficiently. 4. There are some methods preventing explants browning. The article here studied pretreatment and on explants, adding reducer or sorbent to culture medium. It was found that the pretreatment and addition of vitamin C and active carbon made little effects on browning prevention. Further more, polyvinylpyrrolidone (PVP) could prevent browning in a certain extent. However,when heat shock duration was 5min and 2min, the browning degree were much lower. E 5min of heat shock duration with the temperature 450C was more efficiently in browning prevention(see from Figure 5.1).