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. Crosstalk
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.