WATER RELATION PARAMETERS IN VITIS-VINIFERA L IN DROUGHT PERIOD - EFFECTS OF LEAF AGE

The aim of this study was to evaluate the influence of leaf age on phy siological mechanims adopted by grape vines (Vitis vinifera L) in orde r to sustain a favourable growth and production under drought conditio ns. The relationships between the water, turgor, osmotic potentials an d leaf water content were studied during leaf ontogeny using both the pressure/volume and the psychometric technique. The symplasmic water f raction of the total water content decreased with leaf age. The capabi lity for osmoregulation was almost the same in immature and mature lea ves but decreased in old leaves. The calculated volumetric modulus of elasticity increased rapidly with leaf maturity and seems to be the do minant strategy for adaptation to drought conditions.