The role of salicylic acid and gibberellin signaling in plant responses to abiotic stress with an emphasis on heavy metals.

Salicylic acid (SA) and gibberellins (GAs), as two important plant growth hormones, play a key role in increasing plant tolerance to abiotic stress. They contribute to the increased plant antioxidant activities in ROS scavenging, which is related to the enzymes involved in HO-detoxifying. In photosynthetic cycles, the endogenous form of these phytohormones enhances photosynthetic properties such as stomatal conductance, net photosynthesis (PN), photosynthetic oxygen evolution, and efficiency of carboxylation. Furthermore, in cell cycle, they are able to influence division and expansion of cell growth in plants under stress, leading to increased growth of radicle cells in a meristem, and ultimately contributing to the increased germination rate and lengths of shoot and root in the stress-affected plants. In the case of crosstalk between SA and GA, exogenous GA can upregulate biosynthesis of SA and consequently result in rising levels of SA, enhancing plant defense response to environmental abiotic stresses. The aim of this paper was to investigate the mechanisms related to GA and SA phytohormones in amelioration of abiotic stress, in particular, heavy metal stress.