Impacts of Drought and/or Heat Stress on Physiological, Developmental, Growth, and Yield Processes of Crop Plants

Drought and heat stress are among the two most important environmental factors influencing crop growth, development, and yield processes. A comprehensive understanding of the impact of drought and heat stress will be critical in evaluating the impact of climate change and climate variability on crop production. Both drought and heat stress influence an array of processes including physiological, growth, developmental, yield, and quality of crop. The objective of this review is to provide an overview of the influences of these two stresses on the above processes independently and in combination. Our review suggests a clear need of information on interactive effects of stresses particularly of drought and heat stress which mostly occur in combination. Both short- and long-term stresses can significantly influence growth and yield processes when stress occurs at sensitive stages. Crops are generally more sensitive to drought and/or heat stress during reproductive stages of development, which mainly influences seed numbers. Some of the important traits associated with drought- and/or heat-stress tolerance are indicated and discussed. The impacts of drought and heat stress are often different, and tolerance mechanisms may also be different. There is a wide range of crop modeling approaches (simple empirical models and more mechanistic models) that try to quantify the impact of stresses on growth, development, and yield and yield quality traits. These crop models should have the capability to quantify the impact of both short- and long-term stress events on growth, development, and yield processes. Modeling growth, development, sink-source relation, grain yield, and grain quality of crops can improve understanding of physiological and genetic nature of tolerance which can lead to increased grain yield and quality of crops. Improved models can enhance our capacity to predict crop performance in future climates and also to identify traits that can potentially be improved or exploited to obtain higher and more stable crop yields under stressed environments.