5Heat Stress and RootsScott A. Heck

5Heat Stress and RootsScott A. Heckathorn, Anju Giri, Sasmita Mishra, and Deepesh BistaAbstractAs with above-ground tissues, plant roots can be subjected to stressful hightemperatures that can limit whole-plant function and decrease crop productivity.Further, with impending climate change, the frequency, duration, and severity ofroot heat stress will increase. In comparison to shoot function, especiallyphotosynthesis, much less is known regarding heat stress and roots. Most previousresearch on roots and heat stress has been conducted on detached roots or byheating only roots or parts of root systems (but not shoots too) in intact herbaceousplants, and most past studies on intact plants have imposed chronic heat stress,with few examining effects of abrupt heat stress (e.g., heat waves). Importantly,plant responses to heat stress often differ in detached roots or when only roots areheated, compared to plants wherein both shoots and roots (or shoots only) areheated, and responses to chronic and abrupt heat stress can differ. Hence, manypast results do not inform as to how natural heat stress often impacts roots in intactplants or do not inform as to the effects of heat waves on roots. Both chronic andabrupt heat stress can decrease root growth and function, including nutrient andwater uptake, and studies in which both roots and shoots were heat-stressedindicate that roots are often more sensitive to heat stress than shoots. Heat stressmay affect roots both directly and indirectly, and indirect effects likely involvedecreases in shoot carbon provided to roots or changes in root water relationsdriven by increased shoot water demand, which then affect root growth andnutrient uptake. Interactive effects between heat stress and other global environ?mental change factors (e.g., elevated carbon dioxide, drought) on roots are likely.We conclude that further research on roots and heat stress is strongly warranted.