Mechanisms involved in diurnal changes of osmotic potential in grapevines under drought conditions

The aim of this study was the quantitative determination of the contribution of various possible mechanisms involved in diurnal changes of osmotic potential in grapevine leaves (Vitis vinifera L., cv. Victoria) under water stress conditions. Results of this study revealed that dehydration accounted for 36 % of the diurnal changes in osmotic potential in stressed plants. The relative contribution of changes in non-osmotic volume was negative. Net solute accumulation accounted for 73 % of the diurnal changes, indicating the occurrence of an active osmotic adjustment during the day in stressed plants. There was evidence that compounds other than sugars contributed to diurnal osmotic adjustment in stressed grapevines.