Studies On Preventive Technique And Browning Mechanism In The Tissue Culture Of Cymbidium Longibracteatum 'Cui-xian' Flower Stalks

In this paper, flower stalks of Cymbidium longibracteatum 'Cuixian'were used as explants, the mechanism of browning were studied via measuring the changing of PPO, POD activity and total phenol contents in different tissue culture time with different methods. the aim of the present study was to provide theoretical and technical basis for controlling browning in tissue culture of Cymbidium longibracteatum. At present the main findings were as follows:1. February was the best time for drawing material with the lowest browning rate being 20%, PPO activity of explants reached the first peak in the first 7 days, later decreased, then PPO activity reached the second peak after the explants inoculated in medium for 21 days, comparing with the best treat, Both differs 3 percent.2. Comparing with the contrast, a difference of 15 percent was showed in the degree of browning after dark culture, the difference was markedly significant.3.Scorbic acid and citric acid could be highly efficient for controlling browning, the anti-Brown was the best when the concentration of scorbic acid and citric acid is 3 g/L, scorbic acid was better.4. PPO and POD activity reached a peak in the first 3 days and 7 days when anti-oxidants or adsorbent was added, enzymatic activity didn't changed with the prolonging of the time. PPO and POD activity and browning rate were the lowest when scorbic acid and citric acid is 3 g/L.5. The activity of PPO and POD decreased with the rising of incision closure temperature. enzymatic activity did not rise with the time of inoculation increasing, PPO activity, POD activity was highest when incision closure temperature was 45℃,there was 2 percent difference between the highest and the lowest PPO and POD activity.6.The browning rate was the lowest being 15% when explants inoculated in 1/2MS medium; while the browning rate was the highest being 35% when inoculated in 1/4MS. Which indicated that low-salt, ammonia nitrogen can reduce explants browning. In addition, a higher ratio of cytokine auxin may also reduce browning to some extent.