Plant hydraulic traits influencing crop production in water-limited environments

Annual crops commonly experience production losses due to soil water limitation and increased vapor pressure deficit (VPD). Crop species and genotypes vary in their ability to sustain production during drought, which reflects variations in drought resistance mechanisms. In this review, we discuss the critical influence of water transport (hydraulic conductances and stomatal traits) on the ability of crops to avoid and tolerate drought, thus sustaining yield. We also summarize scientific gaps to be addressed in the future. Limited transpiration traits, including reduced stomatal density/conductance and increased stomatal sensitivity to soil drought and high VPD, constitute important drought avoidance mechanisms. Drought avoidance is suggested to result in soil water conservation for the critical reproductive stage and yield stability under moderate and terminal droughts. As crop fields experience increasingly drier soils and greater VPD, tolerance mechanisms might become critical to crop production. Osmotic adjustment stands as an important tolerance mechanism that improves crop production during severe droughts. Preventing xylem embolism and/or refilling embolized xylem upon rehydration represent drought tolerance mechanisms critical for plant survival during drought, but their contribution to crop production during droughts is unknown. Time for hydraulic failure combines drought avoidance and tolerance, and its importance for crop production during moderate and severe droughts should be assessed.