Effects of tropospheric ozone on groundnut (Arachis hypogea L.) cultivars: Role of plant age and antioxidative potential

Abstract

Ozone (O3) is a secondary atmospheric pollutant present in the tropospheric environment. Ozone enters in internal tissue of leaf through stomata and produces reactive oxygen species (ROS) which damages cellular membrane, alter gene expression and metabolic activities and ultimately caused death of the plant tissues. Certain defensive mechanism occurs in the internal part of leaves to eliminate generated ROS. However, there is significant change in the levels and kind of defence traits as plants develop from the seedling to juvenile to mature and senescent stages. A field study was conducted for two consecutive seasons with five cultivars of groundnut (Arachis hypogea L cv. TG-37A, TPG-41, TAG-24, GG-20, and Dh-86) to assess the intra-specific variation in defensive response against ozone at various plant developmental stage. Results of the study showed that ozone significantly affected biomass and primary metabolites, generate ROS and increases membrane permeability in all the groundnut cultivars. In response to ROS, groundnut cultivars produced non-enzymatic and enzymatic antioxidants. Study found that the severity of the effect varied among the cultivars and by developmental stages. Cultivar Dh-86 showed higher antioxidative activity and least biomass sensitivity to ozone. Although accumulation of non-enzymatic antioxidants was present to provided defence against ozone, activity of enzymatic antioxidants varied at different growth stages and corresponds to the biomass sensitivity. Study concluded that the ozone phytotoxicity is dependent on the antioxidative potential of the cultivars and the growth stage of the plant. Further, the activity of APX played a measure role for age dependent plant sensitivity in groundnut.