Effects of drought regimes on growth and physiological traits of a typical shrub species in subtropical China

Abstract

Drought represents the most important limiting factor controlling performance of subtropical plants, leading to reduced growth and die-offs. However, the mechanisms underlying growth and physiological responses of subtropical woody plants to different types of drought are poorly understood. Here, potted seedlings of a typical evergreen shrub species Ardisia lindleyana D. Dietr. in subtropical China, were exposed to three water regimes: well watered (WW), fast drought (FD) and slow drought (SD) until death. Leaf gas exchange and water potential were measured over the experimental period. Dry mass production and allocation, leaf nitrogen and carbon isotopic composition, and non-structural carbohydrates (NSC) were measured at mortality. Results showed that growth, leaf water potential and photosynthesis were significantly reduced in both drought regimes. FD induced significant increase of root soluble sugars, but promoted significant depletion of leaf and root starch, finally displaying depletion of root NSC. By contrast, SD led to significant depletion of stem and root starch, whereas the accumulation of soluble sugars in stem and root was significantly higher than that of WW, thereby resulting in no significant change of NSC. Neither FD nor SD has affected leaf carbon isotopic composition or nitrogen concentration at mortality. Our results demonstrate the divergent effects of two different drought treatments on carbon and water economy of A. lindleyana, which may have implications for understanding the mortality mechanism of understory plants in subtropical forests in China.