Elucidating the role of melatonin or sugar beet pulp pellet in physiological improvement characteristics and promoting the growth of Moringa oleifera under lead stress

Abstract

Pot experiments were conducted to evaluate the effect of root and foliar uptake of Pb on Moringa oleifera plants. The levels of Pb used in the experiments were 100 and 400 ppm Pb. The lead application affected the growth, photosynthetic pigment, carbohydrates, proline, oxidative stress biomarkers, mineral contents, and Pb accumulation in Moringa plants. The growth parameters, chlorophyll, Na, K, and Ca content declined in the case of soil or foliar Pb application. The foliar lead application revealed a more negative effect on the growth of moringa plants than the soil application. However, Pb-stressed moringa plants increased carbohydrates, proline, H2O2, MDA, electrolyte leakage, Pb, and Mg content. In addition, the possible role of melatonin (MEL) and sugar beet pulp pellets (SBP) in ameliorating lead toxicity and enhancement of phytoremediation was investigated. It was found that supplemental addition of MEL or SBP increases the growth parameters, photosynthetic pigments, carbohydrates, proline, and minerals compared to stressed moringa plants. Moreover, a decrease in hydrogen peroxide, lipid peroxidation, and electrolyte leakage was observed under MEL and SBP treatments. The ameliorating effect of SBP was more pronounced than that of MEL. Furthermore, MEL application enhanced the phytoremediation capacity of moringa plants.