Use of Nitric Oxide and Hydrogen Peroxide for Better Yield of Wheat (<i>Triticum aestivum</i> L.) under Water Deficit Conditions: Growth, Osmoregulation, and Antioxidative Defense Mechanism

The present experiment was carried out to study the influences of exogenously-applied nitric oxide (NO) donor sodium nitroprusside (SNP) and hydrogen peroxide (H₂O₂) as seed primers on growth and yield in relation with different physio-biochemical parameters, antioxidant activities, and osmolyte accumulation in wheat plants grown under control (100% field capacity) and water stress (60% field capacity) conditions. During soaking, the seeds were covered and kept in completely dark. Drought stress markedly reduced the plant growth, grain yield, leaf photosynthetic pigments, total phenolic content (TPC), total soluble proteins (TSP), leaf water potential (&#936;_w), leaf turgor potential (&#936;_p), osmotic potential (&#936;_s), and leaf relative water content (LRWC), while it increased the activities of enzymatic antioxidants and the accumulation of leaf ascorbic acid (AsA), proline (Pro), glycine betaine (GB), malondialdehyde (MDA), and H₂O₂. However, seed priming with SNP and H₂O₂ alone and in combination mitigated the deleterious effects of water stress on growth and yield by improving the &#936;_w, &#936;_s, &#936;_p, photosynthetic pigments, osmolytes accumulation (GB and Pro), TSP, and the antioxidative defense mechanism. Furthermore, the application of NO and H₂O₂ as seed primers also reduced the accumulation of H₂O₂ and MDA contents. The effectiveness was treatment-specific and the combined application was also found to be effective. The results revealed that exogenous application of NO and H₂O₂ was effective in increasing the tolerance of wheat plants under drought stress in terms of growth and grain yield by regulating plant&#8722;water relations, the antioxidative defense mechanism, and accumulation of osmolytes, and by reducing the membrane lipid peroxidation.