The availability of water has a direct effect on photosynthesis. The density of vines determines the water supply for the plants. The results of the study of the dynamics of the parameters characterizing the photosynthetic activity of grapes, under the influence of different density of vines are presented in the article. Studies were conducted on Riesling with a different planting density of the vines. Greater stability of the pigment apparatus was typical of plants grown in a lower density. In variants with a smaller supply area, increased efficiency of the photosynthetic process was accompanied by the accumulation of starch in the leaves. The negative coefficient of the correlation between the content of starch and efficiency of primary processes of photosynthesis may indicate the absence of stress-induced blocking the outflow of plastic substances from the leaves in variants with a lower plant density.