GAS EXCHANGES IN VITIS-VINIFERA UNDER WAT ER-STRESS REGIME .1. CHARACTERIZATION OF THE VARIETY BEHAVIOR

The effects of the application of water stress on the gas exchanges of cultivars of grapevine (Vitis vinifera L.), through measurements of t he photosynthesis and stomatal conductances in isolated leaves and the entire plant, were analysed with the purpose of characterizing the be havior of different cultivars. Plants of 1 to 2 years old, grafted on 'Fercal', potted and cultivated in a green house and phytotron were us ed. The gas exchanges were measured with infrared CO2 analysers, one b eing portable (ADC-LCA3) for the isolated leaves, and a Double Assimil ation and Transpiration Chamber (CAT) for the entire plant. The evolut ion of the water stress greatly reduced the photosynthesis and stomata l conductances of the leaves, revealing different sensitivity levels b etween the cultivars. Two groups were distinguished: a sensitive one, with greater reductions in the carbon assimilation rates, formed by th e cultivars Semillon and Ugni blanc; and the other one, more adapted, represented by the cultivars Alexandria Moschatel, Chardonnay and Arri loba.