The Decrease of Leaf Dark Respiration during Water Stress Is Related to Leaf Non-Structural Carbohydrate Pool in...

Dark respiration (R_d) is a fundamental plant process used to gain biomass and maintain plant physiological activity. It accounts for the metabolization of a large share of the carbon fixed by photosynthesis. However, R_d during conditions of severe plant water stress is still poorly understood. The decrease in leaf transpiration increases temperature, one of the most important drivers of leaf R_d. On the other hand, water stress decreases the pool of leaf carbohydrates, which are the most important substrate for respiration. The aim of the present work was to determine the impact of water shortage on leaf R_d in grapevine and understand the driving factors in modulating leaf R_d response under plant water stress conditions. Water stressed vines had lower R_d as the water shortage severity increased. R_d was correlated with leaf temperature in well-watered vines. Instead, in water stressed vines, R_d correlated with leaf soluble sugars. The decrease of leaf R_d in water stressed vines was due to the decrease of leaf non-structural carbohydrate that, under water stress conditions, exerted a limiting effect on R_d.