Salicylic Acid and its Crosstalk with Other Plant Hormones Under Stressful Environments

Plants face various biotic and abiotic stress environments which induce a coordinated defense response or tolerance to those stress effectors, respectively, by activating the expression of specific genes. Salicylic acid (SA) has a central role in plant tolerance to both biotic and abiotic factors; it facilitates plant pathogen interaction and triggers local and acquired resistance. It is also involved in alleviating abiotic stress aspects such as metal toxicity, drought, high salinity, chilling, and heat. Many effects are detected in plants exposed to abiotic stress conditions in response to SA including increasing antioxidant activity, lowering ROS levels, and restoring stunted growth. SA thus helps mitigating multiple biotic and abiotic stress effects on plants. A multipart crosstalk exists between SA and other plant hormones (jasmonic acid, abscisic acid, ethylene, gibberellic acid, auxin, cytokinin, brassinosteroids, strigolactone, polyamines, and melatonin). This chapter will revise the signal pathways conserved among plant hormones and emphasize the crosstalk between SA and different plant hormones under stressful conditions.