[Changes of non-structural carbohydrates in Caryopteris mongolica seedlings during the process of drought-induced mortality].

The changes and distribution of non-structural carbohydrate (NSC, including soluble sugar and starch) content in different organs of one-year-old Caryopteris mongolica seedlings were investigated under suitable water condition (CK), slow-dying drought stress, and fast-dying drought stress. There was no significant difference in soluble sugar content of all organs between slow-dying drought stress and CK. With the extended duration of drought, the soluble sugar content in stem increased firstly and then decreased, while starch and NSC contents decreased. The soluble sugar content in coarse roots decreased, while starch and NSC contents increased. The soluble sugar content in leaves increased, while starch and NSC contents of leaves decreased. The NSC content of leaves, stems, coarse roots and fine roots were 6.2%, 7.8%, 8.3% and 7.4% at the death time (80 days), respectively. Under fast-dying drought stress, soluble sugar content in all organs was higher than that in CK, while starch and NSC contents were lower than that in CK. With the increasing time, soluble sugar content of roots decreased, while starch and NSC contents increased. The soluble sugar, starch and NSC contents in stems increased. The soluble sugar content of leaves increased, while starch and NSC contents decreased. The NSC content of leaves, stems, coarse roots and fine roots were 5.9%, 6.6%, 8.9% and 7.7% at lethal time (30 days), respectively. Under different drought stress, non-structural carbohydrates among different organs of C. mongolica seedlings showed different dynamics. Under slow-dying drought stress, NSC gave priority to allocate energy for maintaining physiological metabolism of organs. Under fast-dying drought stress, NSC mainly maintained plant metabolism in the form of soluble sugar, regulated osmotic potential, promoted water absorption, and coped with drastic drought stress.