Alleviating Effects Of Exogenous Selenium On Dendrobium Candidum Seedlings Under Low Temperature Stress And The Change Of Its Antioxidative Physiology Characteristics

Three different strains (’ZD-1’,’ZD-2’,’ZD-3’) of Dendrobium candidum seedlings were sprayed with different concentrations sodium selenite (Na2SeO3) solution on leaves and treated with low temperature stress at0℃for6and12h and recovery growed for6d. In order to discuss the effects of exogenous selenium on cold tolerance and recovery growth ability of Dendrobium candidum seedlings and their relationship with the relevant antioxidant physiological indexs,the malondialdehyde (MDA) content, chlorophyll and carotenoid content, catalase (CAT), peroxide enzyme (POD) and ascorbate peroxidase (APX) activity,AsA, GSH, proline, soluble carbohydrate and soluble protein content in leaves were determined respectively. The main results were as follows.1. In the leaves of Dendrobium candidum under low temperature stress, the content of MDA increased as the chlorophyll and carotenoid content decreased along with the low temperature increase. The activity of CAT, POD and APX increased in the cell which could effectively clean the active oxygen produced by the low temperature. And the increase of proline and soluble carbohydrate and soluble protein content was to improve the osmotic regulation ability of the plant, while the abilities of low temperature resistance enhanced.2. Appropriate concentration of exogenous selenium(0.05～0.10mg·L-1) spraying treatment could alleviate the effect of chlorophyll degradation, also caused seedling antioxidant enzymes (APX, GSH-AsA) activity significantly increase, meanwhile it increased the proline content and decreased the MDA content, improved the cold tolerance of Dendrobium candidum seedlings. However, the high concentration of exogenous selenium(≥0.20mg·L-1) treatment leaded to an opposite result that reduced the cold tolerance of seedlings.3. After low temperature stress treatment, exogenous selenium also had certain influence on antioxidative capability of Dendrobium candidum seedlings which in its recovery growth period. Furthermore, the exogenous selenium caused the AsA of seedlings decrease significantly, but could promote the synthesis and accumulation of GSH. Exogenous selenium(0.10mg·L1) treatment could effectively protect the comprehensive antioxidative capability of Dendrobium candidum seedlings in recovery growth period.4. The variation of the content of MDA,chlorophyll and carotenoid,proline, soluble carbohydrate and soluble protein content in Dendrobium candidum leaves was coincident with low temperature stress. It suggested that those physiological indices could be used as efficient and robust indices of low temperature resistance for Dendrobium candidum plant.In conclusion, appropriate concentration of exogenous selenium(0.05～0.10mg·L-1) could improve the ability of antioxidative system through GSH-As A, meanwhile it decreased the ROS content and reduced the oxidative damage.In practice, it’s essential to spray selenium on Dendrobium candidum cultivation improving ability of antioxidative and the survival rate of tissue cultured seedlings.