Effects of Ozone on Primary Determinants of Plant Productivity

摘要

The study evaluated the relationships among ozone exposure, gas exchange, chlorophyll fluorescence, and whole plant productivity for Spinacea oleracea. Lactuca sativa, Zea mays, Cucumis pepo, and Raphanus sativus in a greenhouse with plants grown hydroponically (spinach) or in loose media (other species) to allow recovery of root systems. Spinach showed decreases in stomatal conductance and transpiration, with variable exposure producing greater effects than constant exposure. Net photosynthesis was affected by ozone less than were the gas exchange parameters. Radish was the only species showing consistent ozone effects with reductions in both shoot and root dry weight. Gas exchange was not consistently correlated with productivity. Chlorophyll fluorescence measurements were stable and reproducible, but changes in fluorescence induced by low ozone levels were not easily observed. The study clearly showed that even though changes in gas exchange and plant productivity occur with ozone exposure, the relationships among them are difficult to detect.