Effect of ozone on photosynthesis and seed yield of sensitive (S156) and resistant (R123) phaseolus vulgaris L. genotypes in open-top chambers

Abstract

Rising tropospheric ozone (O3) concentrations have been identified as a significant threat to crop production. In the present study two snap bean (Phaseolus vulgaris L.) genotypes with known difference in sensitivity to O3 namely S156 (sensitive) and R123 (resistant) were compared with respect to their response to O3 using an Open-Top chambers to throw light on the physiological and biochemical basis of O3 effects. Seedlings were exposed to two different controlled levels of O3 (0 and 80 nmol mol−1 ). Chlorophyll a fluorescence and photosynthetic gas exchange were measured in parallel throughout the growing season. Yield data were collected at physiological maturity. The physiological O3 induced effects were evident long before visible damage appeared in the S156 genotype. Photosynthesis was largely inhibited in the S156 genotype, mainly due to inhibition of the photosynthetic electron transport chain, resulting in decreased reduction of end electron acceptors with consequential reduced carboxylation efficiency and regeneration capacity of RuBP. The seed yield data corresponded well to the photosynthetic response of the test plants.