The exogenous application of salicylic acid and biochar to mitigate chromium stress in Salvia hispanica L.

Abstract

Heavy metal contamination, particularly chromium (Cr) stress, poses a serious threat to agricultural productivity and food safety because of its toxic effects on plant growth and metabolism. This study investigated the individual and combined effects of salicylic acid (SA) and biochar in mitigating chromium-induced stress in Salvia hispanica L. under controlled pot conditions. Plants were exposed to different chromium concentrations (0, 50, 100, and 150 µM), together with foliar application of salicylic acid (10 µM) and soil application of biochar (2%), either individually or in combination. Chromium stress significantly reduced morphological parameters, biomass accumulation, and photosynthetic pigment content, indicating substantial oxidative and physiological damage. However, the exogenous application of SA (10 µM) and biochar (2%) significantly alleviated Cr toxicity by improving growth attributes, chlorophyll a and b levels, carotenoid content, and overall fresh and dry plant biomass. Among all treatments, the combined application of SA and biochar was the most effective. It produced the greatest improvements in plant height, root length, fresh and dry weights, and pigment stability, even under high Cr stress. The enhanced tolerance was attributed to reduced metal bioavailability and improved soil conditions. These findings highlight the synergistic potential of salicylic acid and biochar as an eco-friendly and sustainable strategy for mitigating chromium toxicity and improving the growth performance of Salvia hispanica L. in contaminated soils.