Maize Grain Extract Enriched with Polyamines Alleviates Drought Stress in Triticum aestivum through Up-Regulation of the Ascorbate–Glutathione Cycle, Glyoxalase System, and Polyamine Gene Expression

Abstract

The potential protective role of priming wheat seeds with maize green extract (MGE) against the stress effects of drought was studied. Pretreatment using MGE, MGE enriched with polyamines (MGEPA), and drought treatments (irrigation deficit of 30% (severe drought) or 60% (moderate drought) versus 90% relative water content of soil as a control) were applied in a factorial completely randomized design. Under moderate drought, pretreatment with MGEPA outperformed MGE and control, while severely stressed plants died even with pretreatments. Both extracts enhanced normal plant growth and yield and mitigated the deleterious effect of moderately stressed plants. Application of both extracts markedly increased photosynthetic efficiency, membrane stability, relative water content, and accumulation of antioxidants, osmoprotectants, trans- and cis-zeatin, polyamines, and their gene expressions, while levels of superoxide (O2•−) and hydrogen peroxide (H2O2), lipid peroxidation, and electrolyte leakage were decreased. Enzymatic antioxidants and glyoxalase system activities were improved in moderately stressed plants and were further improved with pretreatment with both extracts, thus protecting plants from oxidative damage by up-regulation of the ascorbate–glutathione cycle. Glycine betaine, soluble sugars, and proline levels were greatly increased in pretreated plants, thus maintaining membrane stability and photosynthetic efficiency. The interaction between drought and pretreatment using MGEPA was significant in growing wheat plants in dry environments with 60% relative water content of soil.