Drought stress memory and subsequent drought stress tolerance in plants

Drought stress is one of the most important abiotic stresses causing disturbance of the intracellular water relations and leads to growth inhibition, impaired photosynthesis and ion homeostasis, decreased seed germination rate, enhanced production of reactive oxygen species, and eventually, reduced yields. Severe water deficit causes stress and could be lethal for most of plants, whereas mild water deficit or short periods of drought stress may enhance stress tolerance by inducing hardening. In agricultural practice, a priming process is artificially initiated for the plant to sustain a stress situation. Some of the possible mechanisms involved in a plant's recall of stress episode (e.g., drought) and enhanced response to the stressor in the future include: alterations in the levels of key signaling molecules, proteins or transcription factors; changes in chromatin status, such as histone tail modifications or DNA methylation; and expression of miRNAs involved in posttranscriptional gene silencing.