Drought stress-induced leaf senescence in plants: how to detect it and why.

Background: Plant responses to drought stress include a complex variety of processes at the molecular, biochemical, and physiological levels that operate simultaneously in a specific spatiotemporal way at several organizational levels (including organelles, cells, tissue/organs, and the whole-plant level).

Scope: A roadmap is presented to determine whether drought stress leads to leaf senescence using an integrative approach that considers the process at the whole-plant level. This is essential not only for detecting and monitoring the impact of the drought, but also, more importantly, for identifying whether the plant response is leading to leaf senescence and it is therefore adaptive (protective, indicating stress tolerance) or maladaptive (damaging, indicating vulnerability) to the drought stress. This has important implications for optimizing crop yield and quality (thus requiring urgent attention in current agricultural practices), as well as for environmental management and effective conservation strategies. The detection and monitoring of drought-induced leaf senescence will be discussed, disentangling dubious cases. Furthermore, there will be a focus on drought-induced senescence as an integral plant stress response and whether it indicates damage or protection.

Conclusions: This integrative approach has the potential to help detect, monitor, and fully understand leaf senescence as a protective and adaptive process that plants have evolved to withstand drought stress in agricultural and ecological settings. Exploiting this knowledge and transferring it adequately will help improve crop yield as well as current environmental management programs.