Abstract: 【Objective】 The objective of this study is to investigate the effects of waterlogging on canopy structure and photosynthetic characteristics of summer maize under field conditions. 【Method】 Two summer maize cultivars Denghai605 (DH605) and Zhengdan958 (ZD958) were used as experimental materials. Experimental treatments consisted of waterlogging at the third leaf stage for 3 d (V3-3) and for 6 d (V3-6), waterlogging at the sixth leaf stage for 3 d (V6-3) and for 6 d (V6-6), and no waterlogging (CK). The field experiment was performed to explore the effects of waterlogging for different durations (3 and 6 days) on photosynthetic intensity, net photosynthetic rate, canopy light transmittance and its hemispheric gray images, and grain yield of summer maize at the third leaf stage (V3) and sixth leaf stage (V6). 【Result】 Results showed that leaf area index was significantly reduced after waterlogging. Waterlogging significantly increased group light transmittance, and led to a remarkable reduction of light interception rate. Group light transmittance of summer maize was more susceptible to waterlogging damage at V3, followed by V6, and damage was increased with the increasing waterlogging duration. The light transmittances of ear layer were increased by 96.0% and 70.2% for V3-6 in DH605 and ZD958, respectively, compared to CK. That ground floor increased by 68.9% and 71.9% for V3-6 in DH605 and ZD958, respectively, compared to CK. Waterlogging significantly decreased group photosynthetic potential (LAD) and net photosynthetic rate (Pn)；The most decrease of Pn of two hybrids was found at V3-6, with 23.5% and 20.3% in DH605 and ZD958, respectively. LAD of V3-6 for DH605 was decreased by 68.5%, 45.0%, 31.6%, 25.0%, and 37.5% at seedling-V6, V6-the twelfth leaf stage (V12), V12-the flowering stage (VT), VT-the milking stage (R3), and R3-the physiological maturity stage (R6), respectively. ZD958 decreased by 62.4%, 37.1%, 25.8%, 21.7%, and 38.5%, respectively. The reduction of LAD and Pn led to the decrease of photoassimilates. Dry matter weight of V3-3, V3-6, V6-3, and V6-6 for DH605 was decreased by 12.4%, 24.8%, 9.3%, and 21.1%, ZD958 decreased by 17.3%, 26.7%, 12.5%, and 23.9%, respectively. In addition, waterlogging decreased harvest index, with the most significant reduction in V3-6 with a decrease of 13.3% and 13.8% for DH605 and ZD958. The degradation of canopy structure and photosynthetic characteristics resulted in a significant reduction of maize yield after waterlogging. Grain yield of V3-3, V3-6, V6-3, and V6-6 for DH605 was decreased by 23.2%, 35.9%, 17.0%, and 22.7%, ZD958 decreased by 20.0%, 35.7%, 15.0%, and 27.1%, respectively. 【Conclusion】 Waterlogging significantly decreased leaf area index and ground photosynthetic potential, led to the reduction of light interception rate and photosynthetic performance, decreasing net photosynthetic rate, eventually resulted in a remarkable reduction of summer maize yield. Canopy structure and photosynthetic characteristics of summer maize was more susceptible to waterlogging damage at V3, followed by V6, damage was increased with the increasing waterlogging duration.

Key words: summer maize, waterlogging, light transmission, net photosynthetic rate, grain yield