Effect of water stress on carbon metabolism of apple plants cultured in vitro

摘要

Under water stress, accumulated assimilates in apple plants cultured in vitro were mainly included as sorbitol and sucrose. The key reason of higher soluble substances in both leaves and roots was the increase of sorbitol under water deficiency stress, which indicated that sorbitol played an important role in osmotic regulation of apple. Higher sucrose contens in both leaves and roots under moderate water deficiency stress indicated that leaves of vitro cultured plants had a stronger osmotic regulating ability than matured leaves of cultivated plants. Starch contents decreased significantly under water deficiency stress and obviously influenced by degrees of water stress, which showed that starch changes also played a certain role in apple plants tolerance to water deficiency stress. The key enzymes of regulating sorbitol metabolism, A6PR and SDH, were much sensitive to water deficiency stress. Process of sorbitol synthesis did not exist in apple roots from the very beginning. Under water deficiency stress, the increase in sorbitol content in apple roots was greatly caused by inhibition of sorbitol degradation, activity of SPS increased significantly under mild stress and moderate stress, the change in the activity was identical with the change in sucrose content Water stress caused ADPGPPase decrease activity, significantly and starch accumulation was influenced. ABA concentration in apple plants cultured in vitro increased rapidly in water stress while KT decreased at a certain degree. Combining the changes in carbohydrate content and activities of enzymes relevant to C metabolism with the dynamic changes in endogenous hormones under water stress at different deficit intensity, results could be obtained that C metabolism of apple plants was a complicated process regulated by several types of plant hormones cooperatively.