Foliar application of pyraclostrobin alleviates oxidative stress and improves carbon assimilation in soybean

Due to its protein and oil content, soybean is an important crop in developing countries like India to combat energy-protein malnutrition. In a field study, soybean plants- foliar treated with pyraclostrobin- were evaluated for carbon fixation efficiency and antioxidant levels response. Pyraclostrobin (F500) was sprayed over soybean leaves on the tenth and twentieth day after the emergence (DAE) of seedlings at concentrations ranging from 0.05% to 1%. Parameters associated with carbon fixation, like photosystem II efficiency, gas exchange parameters, carbonic anhydrase activity, and biomass accumulation, were quantified on the 45th DAE. Antioxidant level and activity of antioxidant enzymes were also analyzed at the same stage. The amount of antioxidants like ascorbate (ASA) and the activity of antioxidant enzymes (i.e., guaiacol peroxidase, ascorbic acid peroxidase, superoxide dismutase, and catalase) decreased after pyraclostrobin application indicating alleviation of oxidative stress in treated plants as compared to control. A significant increase in the rate of photosynthesis was also recorded in the treated plants. Limiting factors of net photosynthesis like chlorophyll content, carbonic anhydrase activity, stomatal conductance, inter-cellular CO2 concentration, and transpiration rate improved after 0.1% F500 treatment. Mitigation of oxidative stress by pyraclostrobin improves the primary metabolism (fixation) in soybean, resulting in enhanced biomass accumulation.