Osmotic adjustment and partitioning of turgor responses to drought in grapevines leaves

The aim of this study was to examine the ability of grapevines (V. vinifera L.) for osmotic adjustment using the pressure-volume technique as well as to evaluate the relative contribution of changes in both osmotic and elasti c properties of leaf tissue in turgor maintenance under drought conditions. Pressure volume analysis indicated a significant increase in symplastic wa ter fraction of the total water content in stressed plants. The calculated decrease in osmotic potential due to net solute accumulation in stressed gr apevines was 0.55 MPa, suggesting that osmotic adjustment constitutes an im portant drought tolerance mechanism. Partitioning of turgor responses to dr ought into its components, revealed a negative contribution of elastic adju stment in turgor maintenance of stressed grapevines. Thus, the physiologica l role of tissue elasticity as a beneficial drought mechanism in grapevines might be reconsidered.