Salicylic acid-induced impact on fluorescence kinetics, antioxidant properties, and growth of Amaranthus plant.

Abstract

Plants are unable to grow at their full potential under different environmental stress conditions which could lead to decreased crop productivity. To improve the growth of the plants in such situations, application of fertilizers and agrochemicals are employed by the farmers. However, the application of phytohormones is still under exploration. In this context, in the present study, salicylic acid with different doses (5 µM, 10 µM, 20 µM, 50 µM, and 100 µM) have been used for the foliar application at four days intervals three times to grow Amaranthus plants in pot soil under natural weather conditions. Among all the treated plants it was observed that among all the doses, at 10µM SA there was the maximum increase in the total plant length, leaf number, and fresh biomass by 23%, 16%, and 34%, respectively. The values of the chlorophyll fluorescence matrix also showed a beneficial impact of salicylic acid only up to 20 µM of SA. Further, the level of oxidative biomarkers including SOR and MDA reduced up to 20 µM of SA but H2O2 showed an increasing trend in a dose-dependent manner. To counterbalance the oxidative biomarkers, the application of salicylic acid increased the activities of SOD, POD, APX, and elemental uptake (Ca, Mg, Zn) concentration-wise. However, among the different antioxidative enzymes, CAT showed a different trend by decreasing their activities with increasing doses of salicylic acid. Exogenous salicylic acid also reduced the level of oxalic acid and increased the level of endogenous salicylic acid. Therefore, among the different doses, the lower dose particularly the 10 µM showed a better biomass allocation and qualitative attributes over the control plants. This study would provide a sustainable strategy where the appropriate dose of salicylic acid could be applied to support the plant metabolism in the presence of any stress conditions.