Quality of PAR (photosynthetically active radiation) has major impact on the ability of plants to use its energy for photosynthesis. Prolonged exposure also affects composition and function of the photosynthetic apparatus. In the first experiment was the ratio of the color of the cultivation light red to green to blue 1:1:2 and 2:1:1 (in both supplement IR). By this way propagated plants did not show large differences of functional state of PSII. Therefore, extreme conditions (cultivation light was only blue or only red) were chosen for the second experiment. The results showed that plants grown in blue light have a higher efficiency of photosynthesis. These plants were also able to make better use of high intensity radiation. PAR quality had also short-term effect. Blue light was better used in photosynthetic processes than red light in both cultivation variants (in second experiment).