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 equaldose conditions in closed fumigation chambers under twodifferent ozone (O3) pattern: Var130 (17:00–09:00 h: 40 μg O3 m-3; 09:00–17:00 h: 130μgO3 m-3) and Var220 (16:00-12:00 h: 40 μgO3 m-3; 12:00–16:00 h: 220μg O3 m-3).Control plants were exposed under carbon filtered airconditions (ozone free, CF-control). Sugar beet plants wereexposed four weeks each during 6-leaf-stage and lateralgrowth respectively. Rape plants were exposed for 14 daysduring flowering (f) or as young plants (y). In between andafter the end of exposure, plants were kept in carbonfiltered air (CF; < 10 μg O3 m-3). With respect to sucrose and chlorophyll content of leaves andseed weight, rape plants were most sensitive duringflowering. Under equal dose conditions, the most pronouncedeffects on chlorophyll and sucrose content of leaves as wellas 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 shorttime high ozone peak conditions (Var220). Howeverglucose content in taproots (CF: 100%; Var130: 43%;Var220: 79%) and fatty acid content in rape seeds wasaffected most after exposure to moderate ozone peaks(Var130). Var130-plants seem to recover better fromozone stress than Var220-plants, but glucose content oftaproots and fatty acid content of rape seeds indicate long-lastingeffects especially in Var130-plants.Although experiments were conducted in a closed chambersystem it can be concluded, that current ozone concentrationscan induce adverse effects on these crops.