Leaf photosynthetic characteristics of waxy maize in response to different degrees of heat stress during grain filling

Background In the context of climate change, maize is facing unprecedented heat stress (HS) threats during grain filling. Understanding how HS affects yield is the key to reducing the impact of climate change on maize production. Suyunuo5 (SYN5) and Yunuo7 (YN7) were used as materials, and four temperature gradients of 28degree celsius (day)/20degree celsius (night; T0, control), 32 degrees C/24 degrees C (T1, mild HS), 36 degrees C/28 degrees C (T2, moderate HS), and 40 degrees C/32 degrees C (T3, severe HS) were set up during grain filling to explore the physiological mechanism of different degrees HS affecting photosynthetic characteristics of leaves in this study.Results Results showed that HS accelerated the degradation of chlorophyll, disturbed the metabolism of reactive oxygen species, reduced the activity of antioxidant enzymes, and caused leaf damage. Heat stress induced the down-regulation of photosynthesis-related genes, which results in the decrease of enzymatic activities involved in photosynthesis, thereby inhibiting photosynthesis and reducing yield. Integrated analysis showed that the degree of the negative influence of three HS types during grain filling on leaves and yield was T3 > T2 > T1. The increase in HS disturbed leaf physiological activities and grain filling. Meanwhile, this study observed that the YN7 was more heat tolerance than SYN5 and thus it was recommended to use YN7 in waxy maize planting areas with frequent high temperatures.Conclusions Heat stress during grain filling caused premature senescence of the leaves by inhibiting the ability of leaves to photosynthesize and accelerating the oxidative damage of cells, thereby affecting the waxy maize yield. Our study helped to simulate the productivity of waxy maize under high temperatures and provided assistance for a stable yield of waxy maize under future climate warming.