Hormone balance and abiotic stress tolerance in crop plants

► Hormones play central roles in plant adaptation to changing environments. ► Hormonal cross-talk regulates plant responses. ► Large changes in hormone content can have negative effects on plant growth and development. ► The use of inducible promoters will facilitate the generation of stress tolerance crops. Plant hormones play central roles in the ability of plants to adapt to changing environments, by mediating growth, development, nutrient allocation, and source/sink transitions. Although ABA is the most studied stress-responsive hormone, the role of cytokinins, brassinosteroids, and auxins during environmental stress is emerging. Recent evidence indicated that plant hormones are involved in multiple processes. Cross-talk between the different plant hormones results in synergetic or antagonic interactions that play crucial roles in response of plants to abiotic stress. The characterization of the molecular mechanisms regulating hormone synthesis, signaling, and action are facilitating the modification of hormone biosynthetic pathways for the generation of transgenic crop plants with enhanced abiotic stress tolerance.