Yield penalty of maize (Zea mays L.) under heat stress in different growth stages: A review

Maize (Zea mays L.) would exhibit yield penalties as a result of unfavorable changes to growing conditions. The main threat to current and future global maize production would be heat stress. Maize may suffer heat stress in all the growth stages continuously or separately. In order to manage the impact of climate driven heat stress on the different growth stages of maize, there was an urgent need to understand the similarities and differences on how heat stress affected maize growth and yield in different growth stages. For these purposes, the maize growth cycle was divided into seven growth stages in this review, namely germination and seedling stage, early ear expansion stage, late vegetative growth stage before flowering, flowering stage, lag phase, and effective grain-filling stage, and late grain filling stage. The main focus of this review was on the yield penalty and the potential physiological changes caused by heat stress in different stages. The commonalities and differences in heat stress related impacts on physiological processes in the different growth stages had also been compared and discussed. Finally, a framework was proposed to describe the main influence on yield components in different stages, which would also provide a useful guide for identifying management interventions to mitigate heat stress related declines in yield.