Roles of salicylic acid in selenium-enhanced salt tolerance in tomato plants

Aims Selenium (Se) has been reported to mitigate the harmful effects of salt stress on plants; however, the internal mechanisms remain unknown. Here, the effects of Se supplementation on tomato plants under salt stress were investigated.Methods The biomass, relative electrical conductivity (REC), relative water content (RWC), photosynthetic parameter, inorganic ion contents, malondialdehyde (MDA), soluble sugar and proline contents, as well as the regulation of plant hormones of Se application in tomato plants were investigated after exposure to Se and salt stress treatments.Results Exogenous Se application improved photosynthesis and the water use efficiency (WUE) of tomato plants under salt stress, thereby promoting the growth of tomato plants under salt stress. Se supplementation also maintained the K+ and Na+ homeostasis, reduced the REC, decreased MDA, H2O2 and O(2)(center dot- )contents, and mitigated the oxidative damage caused by salt stress. In addition, exogenous Se increased the salicylic acid (SA) content in tomato leaves and roots via up-regulating the PAL or ICS pathways involved in SA biosynthesis. After pretreatment with the SA inhibitor 1-aminobenzotriazole, the photosynthetic efficiency of tomato plants decreased, plant growth was weakened, and the REC was increased, indicating that the alleviating role of Se on salt stress was abolished.Conclusions Our results clarified the roles of Se and its regulation mechanisms in plant salt stress tolerance and the critical involvement of SA in this process. The study of Se in plant abiotic stress tolerance will give a more theoretical foundation for using exogenous Se in agricultural production to enhance crop growth and yield under adversity stresses.