Yield and Water Use Efficiency Were Enhanced Under Alternate Wetting and Drying Irrigation in Rice Through Improving Leaf Morphology and Physiology

Leaf morphology and physiology play a crucial and indispensable role in crop growth and development. Alternate wetting and drying irrigation (AWD) is widely applied in the rice irrigation system. However, there are few studies on the response mechanism of leaf characteristics to AWD. In this study, two indica rice cultivars, Yangdao 6 and Yangliangyou 6, were selected, and two irrigation methods, AWD and conventional irrigation (CI), were set up to analyse the response mechanism of leaf morphology and physiology to yield and water use efficiency (WUE) under AWD. The results showed that yield and WUE were significantly increased under AWD. In terms of yield, AWD increased the effective and high-effective leaf area index (LAI) and specific leaf nitrogen content at the heading stage, improved the photosynthetic rate and promoted the accumulation and transport of photosynthetic assimilates after flowering. In terms of water use efficiency, AWD inhibited ineffective tillering, regulated stomatal characteristics and increased antioxidant enzyme activity and cytokinin levels. Correlation analysis showed that the percentage of productive tillers, NSC translocation amount and remobilisation, LAI, dry matter accumulation, grain–leaf ratio, leaf morphology (leaf length, leaf width) and leaf physiology (activity of antioxidant enzyme, Z + ZR contents, leaf net photosynthesis rate and specific leaf nitrogen contents) were positively correlated to grain yield and WUE. The results indicate that the improved leaf morphology and physiology of rice under AWD contributed to realise the goal of high grain yield and efficient water use.