The results of studying the influence of mineral fertilizers on the water exchange processes of sunflower under salinity conditions are presented. An important role in regulating the water regime belongs to the mineral nutrition of plants, which contributes to the effective course of physiological processes. The introduction of mineral fertilizers into the soil leads to an increase in the amount of albumins and globulins, which are involved in the processes of water binding. Research results show different physiological effects of nitrogen and phosphorus on the colloidal system of plants depending on the phase of sunflower development. At the same time, phosphorus, providing a continuous increase in the amount of bound water fraction in the general water balance, helps to increase the intensity of protective reactions in plants. The insignificant effect of nitrogen appears only in the second half of the growing season of plants, which is associated with its predominant absorption and utilization in the generative phase of sunflower development. A significant positive effect of nitrogen nutrition on the water-holding capacity of leaf tissues and in the subsequent development of plants. Thus, in the flowering phase, 48 hours after cutting, the leaves of plants from the fresh background retained 6.4%, the saline control - 11.9, the variant with nitrogen 12.3, phosphorus - 14.0, and with a combined nitrogen-phosphorus nutrition - 16.1% water of the original content.