Positive Effects of Exogenous Application of Nitric Oxide on Lipid Composition in Sesbania grandiflora (L.) Pers. under Elevated Conditions of Chromium and EDTA

Heavy metal discharge is a major toxic environmental pollutant that creates highly unsustainable conditions for living organisms. They especially impact plants, where elevated concentrations of heavy metals deter growth and development. In addition, metal toxicity alters the cell membrane composition, which may lead to changes in its physiological activity. This study aims to analyze such alterations caused in the lipid content and fatty acid composition of cell membranes in the plant Sesbania grandiflora, under elevated concentrations of chromium. An experiment was carried out by spiking soil with different chromium concentrations, with and without the presence of ethylenediaminetetraacetic acid (EDTA). In order to identify agents that combat toxicity created by heavy metals, sodium nitroprusside (SNP) (a nitric oxide (NO) donor) was sprayed exogenously on the aerial part of the plant. The changes in the growth of the plant were observed over a period of 3 months, and the initial and final growth of the plant were compared at 30 and 90 days, respectively. GC–MS analysis was performed to identify the fatty acid methyl esters present in the chromium-contaminated plant samples. The experimental data depicted that the fatty acid content, phospholipid content, and glycolipid content decreased with rising concentration of chromium with EDTA, whereas toxicity was further controlled in plants supplied with exogenous nitric oxide through SNP. The lauric acid concentration increased in the presence of heavy metals and SNP compared to long-chain fatty acids. 20 C carbon eicosanoic fatty acids were present at higher levels than 18 C polyunsaturated fatty acids, showing the altered desaturase enzyme function and defective phospholipid synthesis in the endoplasmic reticulum. Since the external application of SNP helps in alleviating chromium stress, this work highlights the usage of NO in effectively combating heavy metal stress in plants.