Responses of antioxidant defenses and membrane damage to drought stress in fruit bodies of Auricularia auricula-judae.

Fruit bodies of Auricularia auricula-judae are often subjected to drought stress and became dormant. The responses of antioxidant defenses and membrane damage to drought stress were investigated in this study. Picked fruit bodies were exposed to sunlight and dehydrated naturally and samples were collected at different levels of water loss (0, 10, 30, 50, and 70%) for determination of electrolyte leakage (EL); contents of malondialdehyde (MDA), ascorbic acid (AsA) and reduced glutathione (GSH); and activities of superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD). Results showed that membrane permeability (assessed by EL) and membrane lipid peroxidation (MDA content) remained unchanged at all levels of water loss studied. Contents of AsA and GSH showed no change at 0, 10 and 30% of water loss, however, both of them increased significantly at 50 and 70% of water loss. SOD activity significantly increased with the rising of water loss from 0 to 30%, reached the peak at 30 and 50% of water loss, and then significantly decreased at 70% of water loss. A gradual increase in POD and CAT activities was observed when water loss rose from 0 to 50%. As water loss went up to 70%, POD activity remained the same as that at 50%, but CAT activity decreased. The results indicate that the increased activities of enzymatic antioxidants (SOD, CAT and POD) and contents of non-enzymatic antioxidants (AsA and GSH) in fruit bodies of A. auricula-judae can effectively scavenge reactive oxygen species, cause no damage to cell membranes as demonstrated by the unchanged EL and MDA content, and contribute to dormancy under drought stress.