Effect of gibberellic acid, potassium nitrate and silicic acid on enzymes activity in cowpea (Vigna unguiculata L. Walp) irrigated with saline water

Abstract

In Indian context, cowpea (Vigna unguiculata L. Walp) is a minor pulse cultivated mainly in arid and semi arid regions. Salt stress is one of the most serious limiting factors for growth and production in most of the crops including cowpea. While silicic, gibberellic acid and potassium nitrate is known to alleviate its adverse effect. Thus, Green house experiment was conducted to investigate the effect of exogenous application of gibberellic acid, potassium nitrate and silicic acid under salt stress on the enzymatic activities in cowpea. The experimental design was factorial completely randomized design with different eight treatment combinations, two level of irrigation to induce salinity stress i.e. tap water (S1) and 4 EC (S2). The plants were sprayed with GA3, KNO3 and silicic acid after 10 and 30 DAS (Days after sowing) and samples withdrawn after 20 and 40 DAS for the analysis. The activities of enzymes were recorded for polyphenol oxidase, peroxidase, nitrate reductase and phenylalanine ammonialyase. The enzymes activities viz., polyphenol oxidase, phenylalanine ammonialyase and peroxidase that increased with increase in concentration of salt however, the nitrate reductase activity decreased. On application of GA3, KNO3 and silicic acid increased polyphenol oxidase, peroxidase, nitrate reductase and phenylalanine ammonialyase enzymatic activity. This investigation has suggested silicic acid, gibberellic acid, potassium nitrate as a potential biomolecules affecting the nitrate reductase as well as ROS scavenging enzyme under abiotic stress like salinity.