ABSTRACT
Water deficit is projected to be intensified by climate change and hydrological cycle imbalance, drastically reducing crop yield and quality as the main human concern for food supply, security, and nutrition. On stress perception, a wide array of signalling pathways targets plant molecular responses by regulating gene expression and transcription factors to modify plant metabolic pathways consist of proteins, hormones, water status, nutrients, chemical compositions as well as physiological, anatomical and morphological characteristics that allow plants to cope with stress. Phytohormone homeostasis and their crosstalk have a crucial role in plant adaptation in all aspects of plant responses from perception, signal transduction, activity of ion-channels, protein modification, protein degradation, and gene expression to control water status, nutrient homeostasis, photosynthesis apparatus and thus plant growth, development, recovery, and survival. The effects of hormones greatly vary depending on their concentrations in specific tissues, cells, cellular compartments, and organs, plant genotype, hormonal interactions, nutrient status, plant phytochemistry, growth stages, environmental conditions, and stress combinations. To promote drought tolerance, multidisciplinary approaches are required to concomitantly emphasis on improving plant performance at the whole plant levels from signalling and gene expression to water, nutrient, hormone, and redox homeostasis, as well as metabolic, physiological, and morphological modifications to elevate crop tolerance to multiple stresses and to optimize photosynthetic efficiency under predicted stress and control conditions. Therefore, this review was undertaken to elucidate the role of hormones and their interactions in response to drought stress to provide up-to-date information required for designing drought tolerant crops.
