Phosphorus sources enhance barley growth and mitigate lead stress via antioxidant responses, proline metabolism, and gene expression

In the present study, we have designed the current experiment to explore the contribution of different sources of phosphorus (P) i.e., single super phosphate (SSP), nitrophoska (NP), and di-ammonium phosphate (DAP) at two different levels i.e., 50 and 100 mg kg(-1) in mediating growth and eco-physiology by alleviating lead (Pb) stress i.e., (100 mg kg(-1)) in cereal crop i.e., barley (Hordeum vulgare L.). Results from the present study showed that the increasing levels of Pb in soils significantly decreased plant growth and biomass, photosynthetic pigments, gas exchange attributes, and P contents from the roots, stems, leaves and nodules. Conversely, increasing levels of Pb in the soil increased oxidative stress indicators in term of malondialdehyde, hydrogen peroxide, superoxide radicle and electrolyte leakage and enzymatic and non-enzymatic compounds and their specific gene expression and proline metabolism including proline, pyrroline-5-carboxylate, pyrroline-5-carboxylate reductase and pyrroline-5- carboxylate dehydrogenase, AsA-GSH cycle including glutathione, ascorbate, glutathione disulfide and dehydroascorbic acid, cellular fractionation including pectin methylesterase activity, uronic acid, hemicellulose I, hemicellulose II, cellulose and pectin methylesterase and also increased Pb concentration in H. vulgare. Interestingly, the application of different sources of P counteracted the toxicity of Pb in H. vulgare, leading to greater growth and biomass. This protective effect is facilitated by the P' ability to sequester reactive oxygen species, thereby reducing oxidative stress and lowering As concentrations in both the roots and shoots of the plants. Our research findings indicated that the application of different sources of P has been shown to enhance the resilience of H. vulgare to Pb toxicity, leading to not only improved biomass but also a better physiological state of the plants.