Effects of Two Different Ozone Exposure Regimes on Chlorophyll and Sucrose Content of Leaves and Yield Parameters of Sugar Beet (beta Vulgaris L.) and Rape (brassica Napus L.)

Sugar beet (Beta vulgaris cv. Loretta) and rape (Brassica napus cv. Licolly) plants were exposed under equal dose conditions in closed fumigation chambers under two different ozone (O3) pattern: Var130 (17:00–09:00 h: 40 μg O3 m −3; 09:00–17:00 h: 130μg O3 m−3) and Var220 (16:0012:00 h: 40 μg O3 m −3; 12:00–16:00 h: 220μg O3 m−3). Control plants were exposed under carbon filtered air conditions (ozone free, CF-control). Sugar beet plants were exposed four weeks each during 6-leaf-stage and lateral growth respectively. Rape plants were exposed for 14 days during flowering (f) or as young plants (y). In between and after the end of exposure, plants were kept in carbon filtered air (CF; < 10 μg O3 m −3). With respect to sucrose and chlorophyll content of leaves and seed weight, rape plants were most sensitive during flowering. Under equal dose conditions, the most pronounced effects on chlorophyll and sucrose content of leaves as well as fresh weight of taproots (CF: 100%; Var130: 97%; Var220: 83%) and of rape seeds (CF: 100%; y: Var130: 122%; Var220: 99%; f: Var130: 84%; Var220: 78%) were detected after exposure under short time high ozone peak conditions (Var220). However glucose content in taproots (CF: 100%; Var130: 43%; Var220: 79%) and fatty acid content in rape seeds was affected most after exposure to moderate ozone peaks (Var130). Var130-plants seem to recover better from ozone stress than Var220-plants, but glucose content of taproots and fatty acid content of rape seeds indicate long-lasting effects especially in Var130-plants. Although experiments were conducted in a closed chamber system it can be concluded, that current ozone concentrations can induce adverse effects on these crops.