The increasing frequency of droughts driven by global warming poses a significant threat to wheat (Triticum aestivum L.) growth and yield. This study investigated stably inherited cuticular-wax mutants of wheat leaf sheaths, generated by ethyl-methanesulfonate (EMS) mutagenesis and isolated through phenotype-based screening. We systematically analyzed physiological responses, leaf sheath wax architecture, and lipid metabolism in a multi-wax mutant (mw; characterized by abundant leaf sheath wax crystals), a low-wax mutant (lw), and the wild type (WT) under both well-watered and drought conditions. Scanning electron microscopy (SEM) revealed a distinctive honeycomb-like network on the mw sheath epidermis, whereas the lw primarily displayed scattered block-like crystals. Under drought stress, lw leaves lost water significantly faster than mw (P < 0.01). Additionally, the mw leaf sheath exhibited significantly higher peroxidase (POD) and superoxide dismutase (SOD) activities, lower malondialdehyde (MDA) levels, and greater proline accumulation than lw (all P < 0.05). Untargeted lipidomics using ultra-high-performance liquid chromatography-mass spectrometry (UHPLC-MS) identified ten major lipid components, with fatty acids representing the largest proportion (25.7%). Aliphatic aldehydes and hydrocarbons were markedly enriched in mw and were positively correlated with drought tolerance indices. Overall, our results suggest that leaf-sheath wax enhances wheat adaptation to drought through the formation of a physical barrier together with modulation of lipid pathways, thereby promoting water retention and antioxidant defense. These findings provide novel metabolic insights into the drought-response mechanisms of leaf-sheath wax and lay a theoretical foundation for breeding drought-resilient wheat cultivars.
Wang et al. (2025) studied this question.