The effect of blue light (BL, bandwidth 420-460 nm) and red light (RL, bandwidth 620-640 nm) on the rates of consumption and evolution of oxygen and rate of heat production of plants after action of high temperature (45degreesC during 30 min) was studied. The rate of heat production was used as indicator of plant resistance to the action of unfavourable factors, since this index reflects the. physiological condition. The object of investigation were the seedlings of summer wheat. The blue light compared with red light had favourable effects on the rates of oxygen metabolism. The rate of O-2 evolution of wheat seedlings with blue light was higher by 50% (optimal temperature) and by 60% (after action 45degreesC temperature) as seedlings with red light. The rate of oxygen consumption of seedlings treated by high temperature with blue light was inhibited. by 40-45% as control, whereas this index was decreased by 75% in plants after temperature shock with red light. Heat production rate of wheat seedlings grown in blue light was higher than the heat production rate of seedlings grown with red light.