Exogenous citric acid improves growth and yield by concerted modulation of antioxidant defense system in brinjal (Solanum melongena L.) under salt-stress

Brinjal is sensitive to salinity, a common factor responsible for reducing its biomass and yield components. Recent research has demonstrated that citric acid/citrates can provide abiotic stress resistance in plants. In this study, Brinjal variety Pusakranti was treated with four concentrations of CA at 0, 100, 200, and 300 ppm applied foliarly under two levels of salt stress (0 mM and 60 mM NaCl) during spring 2021 with four replication per treatment. Salt stress reduced plant growth and yield attributes, pigments as well as metabolites in plants. Antioxidant enzyme activities of the plant increased compared to the non-stressed plants. While 300 ppm CA concentrations oenhanced the shoot and root fresh biomass (75 % and 71.8 %) and dry biomass (82.5 % and 40.7 %), while 200 ppm CA application increased the fruits count by 50 %, fruit diameter by 49 % and leaf photosynthetic pigments by 61 % compared to only salt-stressed plants. Similarly, CA application enhanced the antioxidants both enzymatic and non-enzymatic such as catalase by 42 %, peroxidase by 66 %, superoxide dismutase by 44 %, polyphenol oxidase by 50 % and Glutathione peroxidase by 37 % compared to only salt stressed plants. Furthermore, 300 ppm CA application also promoted the content of primary metabolites such as total protein content by 75 % and total free amino acids by 32 % as well as improvement in secondary me-tabolites such as total phenols by 31 % and flavonoids by 96 % compared to only salt treated plants. Overall, the above described results suggested that the foliarly applied CA(200 ppm) is a proficient approach which effec-tively counteract salt stress in brinjal by improving plant biomass, pigments, primary and secondary metabolites as well as modulating the the antioxidant defense system of the studied plant.