A Study on Techniques of Inducing Callus and Controlling Browning of Stem Segments of Parakmeria lotongensis

Techniques of controlling browning and tissue culture on stem segments of young branches on mature trees of Parakmeria lotongesis were researched.Results obtained showed that 1/2 MS medium and WPM medium were more suitable to tissue culture of Parakmeria lotongensis.A lot of callus were induced on WPM medium containing BA 1.5 mg·L-1,NAA 0.2 mg·L-1 and 2,4-D 1.0 mg·L-1.A large number of adventitious buds and some calluses induced from calluses were observed on WPM medium supplemented with BA 1.5 mg·L-1,KT 0.5 mg·L-1,NAA 0.2 mg·L-1 and 2,4-D 0.3 mg·L-1.The medium of WPM+BA 1.5 mg·L-1+KT 0.5 mg·L-1+NAA 0.2 mg·L-1+IAA 1.0 mg·L-1 was fit to shoot proliferation. Plantlets rooted well on 1/2 MS medium containing NAA 0.3 mg·L-1 and IBA 0.2 mg·L-1 with 1.5 percent active charcoal. The effects of antioxidizer on controlling oxidative browning was better than that of adsorbent.There were difference among various antioxidizers on controlling browning.Their capacities of preventing browning were as follows:ascorbic acid (vitamin C)mecapto ethanoldithiothreitol.Effects of polyvinylpyrrolidone (PVP) and active charcoal on preventing browning were not obvious. Oxidative browning rates of explants on WPM medium supplemented with ascorbic acid (10 mg·L-1),mecapto ethanol (1 mL·L-1) and dithiothreitol (0.5 mg·L-1) were 67%,53% and 33% lower than that of without any antioxidizer in initial culture and subculture.The treatment that explants were putfor 2 h at 4 ℃ before inoculation favor the decreasing browning, esplants browning rate decreased from 35% (CK) to 25%.