Low-nitrogen-tolerant maize cultivar improves photosynthesis and yield by optimizing nitrogen allocation to increase electron transport under low-nitrogen and low-light stress
Qinlin Liu, Yunbo Guo, Pijiang Yin, Tianqiong Lan, Gui Wei, Fan Liu, Chengcheng Lyu, Fanlei Kong, Yuan Jichao
Abstract
This study aimed to identify the physiological mechanisms enabling low-N-tolerant maize cultivar to maintain higher photosynthesis and yield under low-N, low-light, and combined stress. In a three-year field trial of low-N-tolerant and low-N-sensitive maize cultivars under two N fertilization (normal N: 240 kg N ha −1 ; low-N: 150 kg N ha −1 ) and two light conditions (normal light; low-light: 35% light reduction), the tolerant cultivar showed higher net photosynthetic rate than the sensitive one. Random Forest analysis and Structural Equation Modeling identified PSI donor-side limitation (elevated Y ND ) as the key photosynthetic constraint. The tolerant cultivar maintained higher D1 and PsaA protein levels and preferentially allocated photosynthetic N to electron transport. This strategy reduced Y ND and sustained photosystem stability, thus improving carboxylation efficiency and resulting in higher photosynthesis.