A Mechanistic Action of Salicylic acid on Metabolic Profiling, Antioxidative Potential, and Growth Pattern of Amaranthus hybridus

This study has been conducted to investigate the effects of salicylic acid application on the growth and biomass of Amaranthus hybridus. The crop was grown in pots during July-August 2023, under natural weather conditions in the botanical garden of Banaras Hindu University, Varanasi. Different doses of SA (0.69 ppm – 13.8 ppm) was sprayed on the shoot of the plants. Compared to the control group, SA application at 0.69 ppm, 1.38 ppm, and 2.76 ppm showed increased growth and yield of the plants. SA applied at 1.38 ppm concentration, particularly, gave maximum increments in the length and biomass of the crop. SA application reduced the formation of oxidative stress markers (H2O2, SOR, MDA) by increasing the activities of antioxidants like SOD, POD, APX, total phenol, and proline. Salicylic acid treatment also increased the nutritive value of the crop by increasing the level of Ca, Mg, Fe, Zn, and protein, while reduced the levels of oxalic acid. The photosynthetic efficiency of the PSII was strengthened better with 1.38 ppm SA application by increasing chlorophyll content, allocation of absorbed light energy to drive the photochemical process, and quenching of the heat energy. The metabolic profiling via UHPLC-Q-TOF-MS/MS revealed increase in the number and proportion of secondary metabolites belonging to phenolic, alkaloids, terpenoid, flavonoids, betalains, and coumarins group by 240%, 127%, 37%, 182%, 83%, and 90% respectively.  Hence, 1.38 ppm of SA has been considered as the suitable dose for spraying on Amaranthus hybridus for increased growth and biomass.