PJB-2019-644
THE ROLE OF SALICYLIC ACID AND GIBBERELLIN SIGNALING IN PLANT RESPONSES TO ABIOTIC STRESS WITH AN EMPHASIS ON HEAVY METALS
ABOLGHASSEM EMAMVERDIAN
Abstract
Salicylic acid (SA) and gibberellins (GA), 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 H2O2-detoxifying. In photosynthetic cycles, endogenous form of these phyto-hormones 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 meristem, and ultimately contributing to the increased germination rate and lengths of shoot and root in the stress-affected plants. SA can lead to the activation of plant defense mechanisms including stimulated expression of the genes involved in antioxidant activity and modulation of cellular redox homeostasis and the alteration in transcription element activities. The mechanisms of GA action when plants encounter abiotic stress, especially metals stress, include reduction of GA levels via increasing Della accumulations. So that Della-mediated responses can lead to the stimulation of antioxidant enzyme activity under stress conditions. In the case of crosstalk between SA and GA, exogenous GA3 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 phyto-hormones in amelioration of abiotic stress, in particular, heavy metals stress.
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