The Exogenous Application of 24‑Epibrassinolide (24‑EBL) Increases the Cd and Pb Resilience in Zea mays (L.) by Regulating the Growth and Physiological Mechanism

Abstract

eavy metals (HMs) at a concentration above the threshold level act as environmental pol lutants and very often threaten the agricultural productivity globally. Finding afordable and environmentally sustainable deliverables to address this issue is therefore a top focus. Phy tohormones alleviate the HMs-induced toxicity and positively infuence the plant growth. Considering the importance of phytohormones, the present study aimed to assess the efect of 24-epibrassinolide (24-EBL; 10 µM) as seed soaking treatment on growth performance of Zea mays (L.) contaminated separately with increasing concentrations (50–400 mg.kg−1) of lead (Pb) and cadmium (Cd). With increasing metal concentrations, growth and plant biom etric criteria were reduced. For instance, Cd at 400 mg.kg−1 soil reduced the germination ef ciency (56%), root (77%) and shoot (69%) dry weight, total chlorophyll (64%), and carotenoid content (45%). Contrarily, both HMs caused increase in stress biomarkers and antioxidant enzymes in seedling. However, exogenous administration of 24-EBL signifcantly enhanced the growth attributes, photosynthetic pigments, proline, MDA, and antioxidant enzyme activ ity while reducing the harmful efects of HMs stress on Z. mays. For instance, 24-EBL (10 µM) improved the germination percentage, root biomass, chl a, chl b, total chlorophyll, and carotenoid content by 16, 21, 17, 34, 18, and 15%, respectively, in 50 mg.Pb.kg−1 soil-treated Z. mays plants. Furthermore, the amounts of proline, MDA, and antioxidant enzymes in foli age of Z. mays were interestingly and dramatically lowered by 24-EBL application. Uptake of metals in plant organs was signifcantly reduced when 24-EBL was applied to Pb- and Cd treated Z. mays. The recent fndings help us better understand how 24-EBL regulates growth and development of Z. mays as well as how it boosts HMs’ resilience, which could increase the possibility of employing 24-EBL to increase Z. mays productivity. Thus, the present fndings confrmed the potentiality of pre-soaking the seed in 24-EBL solution that neutralizes the toxic efects of heavy metals in Z. mays plants. Therefore, it is suggested that applying phytohor mones including 24-EBL in removal of heavy metal stress in plants is the best possible solu tion in sustainable agriculture.