Abstract
Analysis of the photosynthetic activity and the antioxidant capacity was carried out on the perennial forage grasses: English ryegrass (Lolium perenne L.), Tetramis cultivar, tall fescue (Festuca arundinacea Schreb.) Albena cultivar, meadow fescue (Festuca pratensis Huds.) selected population, red fescue (Festuca rubra L.) ecotype Ravnogor and smooth brome (Bromus inermis Leyss.) Nika cultivar. The analysis was performed during the summer and autumn periods of growth and development. As a basic physiological process, photosynthesis is tightly related to the plant tolerance to different stressors. In addition, tolerance to the secondary exerted oxidative stress directly depends on the antioxidant content. The analysis of the antioxidant capacity was performed by the methods of ferric and molybdate reduction. Photosynthetic activity and the amount of photoprotection were determined by chlorophyll fluorescence methods. The results show about a twofold higher increase in photosynthetic activity of the light phase in F. arundinacea, F. pratensis and B. inermis in summer, which increased with about 20% in L. perenne, F. arundinacea, 25% in F. rubra and decreased with about 15% in B. inermis in autumn. However, the levels of photoinhibition were comparatively low, indicating an absence of stress in practice. The antioxidant capacity was five times higher in the smooth brome from the Nika cultivar, as compared with the other grasses. The tall fescue from the Albena cultivar had the highest photosynthetic activity, uninhibited during the measurements under the high, as well as the low temperatures.