The grapevine cultivars, even in the same family, showed differences in photosynthetic rate, ET rate, stomatal conductivity, CO_2 concentration in cell spaces and water-use efficiency. Those might be due to the results of selection conducted for seedlings to suit the light conditions in the cultivated areas, and, even on the level of variety, variation on light requirements might be produced. Among tetraploid and diploid varieties, there were little differences in the responses of photosynthetic rate, ET rate, stomatal conductivity, CO_2 concentration in cell spaces and water-use efficiency to light intensity. Therefore, no relation between those physiological responses and ployploidy was found.