The effect of different doses of radiation on the content of photosynthetic pigments, gas exchange parameters, and the activity of the enzyme nitrate reductase (NR) in leaves was studied during the ontogenesis of the cotton plant. The obtained results show that γ-rays have a retarding effect on the rate of photosynthesis and the amount of photosynthetic pigments in doses above 100 Gy, and a regulatory effect in doses of 5-50 Gy. It was found that at these doses, the rate of photosynthesis and the amount of pigments increase in the phase of true leaf formation (TLF), this increase continues weakly in the budding (BP) and flowering (FP) phases, and it gradually decreases in the seed ripening or boll opening phases (BOP). The amount of carotenoids, unlike chlorophylls, increases in all stages of plant ontogenesis at high radiation doses. All this indicates that γ-radiation has a stimulating effect on the activity of NR in the leaves of higher plants, leading to high yield.