Responses of water use in moso bamboo (Phyllostachys heterocycla) culms of different developmental stages to manipulative drought

Abstract

Background: Understanding the mechanisms underlying plant water use in response to drought is critical to predicting the trend of ecosystem development under a changing environment, while the responses of water use in clonal plants with interconnected ramets to drought are far less clear than trees. Method: In this study, we conducted manipulated drought by excluding 50% annual throughfall at a stand level in a Moso bamboo (Phyllostachys heterocycla) forest, to determine how water use of the Moso bamboo responds to drought stress, and whether bamboo culms of different developmental stages show synchronized responses given the existence of physiological integration. Three developmental stages of bamboo culms (i.e., young, mature and old) were investigated and measurements were made on sap flow density (Js), leaf water potential at predawn (ψpre) and midday (ψmid), leaf water potential at turgor loss (ψTLP), leaf stomatal density and size, and the maximum stomatal conductance (gw(max)) was calculated. Results: Under the manipulative drought conditions, the values of Js significantly decreased in the mature culms but not in the young and old culms. gw(max) remained unchanged in mature culms, and increased in the young and old culms. Drought significantly reduced ψmid of the young culms, resulting in more negative ψTLP in the young culms compared with the old ones. Conclusions: The results imply that the young culms adopted the drought tolerance strategy, while the old culms tended to adopt the drought avoidance strategy. Both the young and old culms are capable of maintaining relatively stable Js under drought by structural and physiological adjustments. Our findings demonstrate the variable responses of water use in bamboo culms of different developmental stages to drought, suggesting an unsynchronized responses of water use to water stress among culms in clonal plants.