Differential Transpiration of Soybean Plants Subjected to a Combination of Water Deficit and Heat Stress Under Field Conditions

A combination of drought and heat stress is highly disruptive to crop yields worldwide. Previous studies of this stress combination were primarily conducted under controlled growth conditions, revealing that it resulted in the activation of unique molecular and physiological stress responses. However, whether similar responses to a combination of drought and heat stress occur under field conditions remains largely unknown. Here we report on a two-year field study of the transcriptomic and physiological responses of vegetative and reproductive tissues of soybean (Glycine max) to water deficit, heat treatment, and their combination. Our findings reveal that the transcriptomic responses of soybeans grown in the field are different from those grown under controlled growth conditions. These differences were especially noticeable in plants subjected to the heat or water deficit treatments, and less in plants subjected to the combination of these stresses. In addition, we report that differential transpiration between leaves and pods, that was originally discovered in plants grown under controlled growth conditions, occurs in field-grown soybeans in response to heat stress, as well as heat stress combined with water deficit. Our findings identify novel transcriptomic patterns unique to field-grown plants and highlight the need for more omics and physiological studies of crops grown under field conditions.