Wplyw stresu wodnego na parametry wymiany gazowej, indeks zielonosci lisci (SPAD) oraz plonowanie wybranych odmian zycicy trwalej i kupkowki pospolitej uprawianych na glebie mineralnej

A greenhouse pot experiment was performed at two soil moisture levels: 70% field water capacity (optimum moisture content) and 35% field water capacity (water stress) to study physiological responses and yield of perennial ryegrass ('Maja', 'Argona') and orchard grass ('Dala', 'Areda'). Rates of photosynthesis and transpiration were measured during vegetation with a Li-Cor 6400 gas analyzer, and chlorophyll concentration was determined with a SPAD-502 chlorophyll meter. The plants were defoliated three times during the vegetation season. It was found that a decrease in soil moisture from 70% to 35% reduced the rate of photosynthesis by an average of 25%. The strongest response was recorded in the cv. 'Maja', where the rate of photosynthesis decreased by 33%. Perennial ryegrass evaporated more water than orchard grass, and water deficit considerably limited the transpiration. Water stress did not cause any significant changes in chlorophyll concentration in leaves of perennial ryegrass cultivars, whereas in orchard grass higher chlorophyll content was observed under water deficit. All cultivars of both species compared in the study responded by yield decrease to a lower soil moisture. The strongest response was noted in cv. 'Dala', where yield decrease was 66%, as compared with control. Photosynthesis and transpiration bad significant effects on dry matter yield and a close correlation was observed between the intensity of photosynthesis and transpiration.