Inhibitory effects and its physiological mechanism of heat shock on tissue culture browning in Phalaenopsis.

In order to find out the physiological mechanisms of heat shock on explant browning in Phalaenopsis, the effects of heat shock on browning degree, the parameters of phenolic and reactive oxygen metabolism were investigated, which employed P. amabilis BL.‘Jude Butterfly’（B3）tissue culture seedling as the experimental material. The results showed that browning degree of leaf explants decreased significantly after heat shock. Moreover, total phenolic content and activities of phenylalanine ammonialyase (PAL) and polyphenol oxidase (PPO) were also lower than the control, it suggested that heat shock treatment effectively alleviated the tissue culture browning by reducing the activities of PAL and PPO in leaf explants of Phalaenopsis, which inhibited the synthesis and oxidation of phenolic compounds, and then decreased quinones content for browning. However, inhibitory effect of heat shock on peroxidase (POD) activity was not obvious. On the other hand, heat shock treatment could affect the oxidative system by means of promoting the activity of superoxide dismutase (SOD) and ascorbate peroxidase (APX) of leaf explants, which led to the decrease of malondialdehyde (MDA) and hydrogen perodixe (H2O2) content, thus protected the cell memberance stability. So it infers that heat shock treatment can effectively suppress tissue culture browning in Phalaenopsis.