Abstract: The aim of this study was to elucidate the effects of straw mulching on active oxygen metabolism in wheat at the grain-filling stage. The overall aim of this research is to identify the most suitable straw mulching method for high-yield dryland cultivation of wheat in Western Henan Province. The wheat variety Yumai 49-198 was used as the experimental material, and was mulched with straw at five different rates [no mulching as the control (I), and 2000 (II), 4000 (III), 6000 (IV) and 8000 kg·ha^-1 (V)]. We determined the reactive oxygen species content in the flag leaf, antioxidant enzyme activity, contents of antioxidant compounds and osmotic regulators, and yield at different times (0, 10, and 20 days) after the heading stage of wheat. It was found that straw mulching decreased the contents of the superoxide free radical ($O^{-·}_{2}$), hydrogen peroxide (H₂O₂), and malondialdehyde (MDA) in the flag leaves of wheat after heading. Treatment IV had the strongest effect; at 20 days after heading, the 2-year average decrease in $O^{-·}_{2}$, H₂O₂, and MDA contents were 43.0%, 32.2%, and 30.4%, respectively, compared with the control. The contents of soluble sugars, amino acids, glutathione, and ascorbic acid, and the activities of superoxide dismutase, peroxidase, and catalase were increased by mulching; the highest 2-year average increases in these indexes were in treatment IV (28.3%, 120.5%, 110.5%, 11.6%, 44.7%, 47.6%, and 57.5%, respectively, compared with the control). The values of these indexes were higher in treatment IV than in the other mulching treatments, and differed significantly from the control. Within a certain range of straw mulching (2000-6000 kg·ha^-1), the increase or decrease in each index was proportional to the amount of mulching, but this relationship was less clear when the quantity of mulch exceeded a certain level. The results showed that an appropriate amount of straw mulch could improve the ability of wheat to scavenge reactive oxygen species, reduce the accumulation of reactive oxygen species, and increase yield. For wheat cultivated in the dryland ecological conditions of Western Henan, the best results were obtained by applying straw mulch at 6000 kg·ha^-1.

Key words: wheat, straw mulching, dryland, oxidation resistance