Low Nitrogen with Split Application Strategy Enhances Antioxidative Defense, Photosynthesis, and Enzymatic Activities to Waxy Maize Under Heat Stress
摘要
Recently, the increasing frequency and severity of heat stress (HS) have severely inhibited growth and production of waxy maize. Whether nitrogen (N) can mitigate the damage caused by HS on waxy maize remains poorly understood and documented. Therefore, the objective of the present study was to evaluate the effects of different N application strategies on heat tolerance mechanisms, growth attributes, and yield traits in two waxy maize hybrids (SYN 2 and SYN 11) during the flowering and early grain-filling stages. HS significantly reduced photosynthetic productivity, enzymatic activity, aboveground biomass accumulation, and yield traits in both hybrids, with more pronounced effects observed in SYN 11. Among various N management strategies, the low split-N treatment N100 + 50 (100 kg N ha–1 at preplant plus 50 kg N ha–1 at the 9-leaf stage) achieved the highest yield and yield components under HS. Specifically, this N strategy increased fresh ear yield by 13.0%, kernel number per ear by 19.3% and fresh kernel weight by, 21.3%, compared to other N treatments across both hybrids. Further analysis using Pearson’s correlations, principal component analysis, and heatmap analysis showed that the alleviating effects of the low split-N treatment N100 + 50 were attributed to enhanced leaf antioxidant enzymes, photosynthetic capacity, and enzymatic activity in kernels. These findings offer new insights into optimizing N management to sustain waxy maize yield under future global warming scenarios.