A glasshouse pot experiment, at two soil moisture levels: 70% ppw (optimal moisture) and 35% ppw (water stress), investigated meadow fescue cultivars (‘Skawa’, ‘Skra’) and timothy cultivars (‘Karta’, ‘Kaba’). Over the vegetation period the intensity of photosynthesis was measured with gas exchange parameters measurement device, Li-Cor 6400, and the content of chlorophyll with the chlorofilometer, SPAD-502, by Minolta. The plants were cut three times. The experiment factors significantly affected the intensity of photosynthesis, content of chlorophyll and grass yielding. Water stress weakened the photosynthetic activity of the cultivars studied. A greater photosynthesis intensity was recorded in meadow fescue cultivars. A greater chlorophyll concentration in leaf blades was observed in plants cultivated under stress. Meadow fescue cultivars contained more chlorophyll in leaf blades than timothy cultivars. A lowered soil moisture resulted in a significant decrease in yielding. Out of all the plants tested, in general a greater yield was obtained from timothy cultivars, ‘Kaba’ especially.

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