Effects of drought on Physiological Responses of Bretschneidera sinensis

Bretschneidera sinensis Hemsl. is a rare and endangered species in China. Understanding the effects of drought on its physiological responses is required for the introduction and protection of this species with future climate change. In order to know the drought effects on plasma membrane permeability (PMP), malondialdehyde (MDA), proline, superoxide dismutase (SOD) and chlorophyll (chl) in B. sinensis, 100 biennial seedlings of B. sinensis were divided into five groups and subjected to different treatments, i.e., a reduction in the amount of water applied on a daily basis. The soluble sugar, soluble starch and nonstructural carbohydrate (NSC) contents were also measured prior to the death of B. sinensis. The results indicated that, as the drought continued and intensified, the proline and SOD contents changed slightly, while the PMP and the MDA content increased constantly, especially under severe drought. The chl content also showed a decreasing trend. Consequently, B. sinensis became highly sensitive to the drought because the repair mechanisms could not keep pace with the damage. When close to death, the B. sinensis seedlings did not use high levels of NSCs. Although, NSCs did not decline, but gradually transferred from leaf to stem and then to roots. Meanwhile, the composition of NSCs changed i.e., soluble starch was degraded to soluble sugar, which indicates an adaptive mechanism in a long-term drought environment. It was concluded that B. sinensis is highly sensitive to the drought because of several physiological changes in B. sinensis, however, carbon starvation would not occur in B. sinensis during drought. (C) 2019 Friends Science Publishers