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

Abstract Aims Selenium (Se) has been reported to mitigate the harmful effect of salt stress on plants, however the internal mechanisms are still unknown. Here, the effects of Se supplementation on tomato under salt stress were investigated. Methods The biomass, relative electrical conductivity (REC), relative water content (RWC), malondialdehyde (MDA), soluble sugar and proline content, and the regulation of plant hormones of Se application in tomato 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 reduced the REC and MDA, decreased the content of H2O2 and O2•−, and mitigated the oxidative damage caused by salt stress. Exogenous Se increased the salicylic acid (SA) content in tomato leaves and roots via up-regulating the PAL or ICS pathways of SA biosynthesis. After pretreatment with the SA inhibitor (ABT), the photosynthetic efficiency of tomato plants decreased, the growth was weakened, and the relative electrical conductivity 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, as well as the critical involvement of SA in this process. The study of Se in plant abiotic stress tolerance will give more theoretical foundation for the usage of exogenous Se in agricultural production to enhance the crop growth and yield under adversity stresses.