The experiment on Zea mays L. cv. Landmark (F1) plants was performed in a greenhouse with UV-B (305–315 nm). The pots with plants were divided into four groups: the first and the second groups were grown, respectively, at low (1.0 kJ m-2 d-1) and high (3.0 kJ m-2 d-1) biological effective dose of UV-B radiation. Half of the pots of each group were sprayed with 0.1% solution of Asahi SL (the third and fourth groups). The intensity of photosynthesis and transpiration, chlorophyll fluorescence, the content of UV-absorbing compounds and radical scavenging activity were measured using DPPH after four and six weeks of UV-B radiation. After six weeks of irradiation with a higher UV-B dose both flavonoid content and antioxidant activity increased by 112% and by 44%, respectively, compared to the plants grown at the lower dose. The plants treated with Asahi SL and exposed to the high dose of UV-B had the content of flavonoids 80% higher than the control ones. Asahi SL decreased scavenging activity in both groups of plants by 17% and 32%, respectively, in comparison with the untreated plants. The intensity of net photosynthesis, the transpiration rate and chlorophyll fluorescence parameters (Fv/Fo, ETR, Rfd) did not differ in most of variants.