Leaf water relations in Diospyros kaki during a mild water deficit exposure

Abstract

The resistance mechanisms (stress avoidance and stress tolerance) developed by persimmon plants (Diospyros kaki L. f. grafted on Diospyros lotus L.) in response to mild water stress and the sensitivity of continuously (on a whole-day basis) and discretely (at predawn and midday) measured indicators of the plant water status were investigated in 3-year old ‘Rojo Brillante’ persimmon plants. Control (T0) plants were drip irrigated in order to maintain soil water content at levels slightly above soil field capacity (102.3% of soil field capacity) and T1 plants were drip irrigated for 33 days in order to maintain the soil water content at around 80% of soil field capacity. The results indicated persimmon plants confront a mild water stress situation by gradually developing stomata control (stress avoidance mechanism) and exhibiting some xeromorphic characteristic such as high leaf relative apoplastic water content, which could contribute to the retention of water at low leaf water potentials. In addition, sap flow measurements made by the heat-pulse technique were seen to be the most suitable method for estimating persimmon water status, because it provided the highest signal intensity (actual value/reference value):noise (coefficient of variation) ratio in almost all intervals of time considered and provides continuous and automated registers of the persimmon water status in real time.