Effects of Different Ratios of Base and Topdressing Nitrogen Fertilizer on the Leaf Senescence and Yield of Insect-resistant Hybrid Cotton Leaf Aging and Reactive Oxygen Species Metabolism of Winter Wheat in Different Cultivation Modes Leaf senescence and active oxygen metabolism of different-type wheats under drought Winter Wheat Flag Leaf Aging and Reactive Oxygen Species Metabolism under Different Nitrogen and Cultivation Modes in Dryland Comparison on the flag leaf aging metabolism of different winter wheat genotypes under three planting models