Effects of combined application of selenium and various plant hormones on the cold stress tolerance of tomato plants

Aims There are few studies on the interaction between selenium (Se) and various plant hormones in mitigating the harmful effects of cold stress on plants. Here, the effects of Se and various plant hormones on Solanum lycopersicum L. (tomato) under cold stress have been investigated to identify a combination of Se and plant hormones that enhances cold resistance. Methods The tomato plants were treated with Se and various plant hormones including salicylic acid (SA), melatonin (MT), and abscisic acid (ABA) respectively. The chlorophyll fluorescence was measured by a Chlorophyll fluorescence IMAGING system. The photosynthetic pigments, malondialdehyde, and sugar contents were measured by an ultraviolet spectrophotometer. Results Among several plant hormones, the co-application of Se and SA was the most effective in mitigating the cold stress of plants. The treatment of Se/SA preserved the plasma membrane integrity and regulated the osmotic substances under cold stress. The interaction between Se and SA modulated some cold-induced genes thereby conferring cold resistance of tomato plants. However, the pretreatment with AIP (SA biosynthesis inhibitor) eliminated the favorable influence of Se on the cold resistance of tomatoes, indicating that regulating the synthesis of SA was one of the mechanisms by which Se enhanced the resistance of tomato plants to cold stress. Conclusions Our results clarified the roles of Se and its regulation mechanisms in plant cold stress tolerance, as well as the critical involvement of SA in this process, which might provide a theoretical foundation for using Se fertilizer to increase crop production under adversity conditions. Highlights The combined treatment of Se with SA, MT, and ABA had better effects on enhancing the cold stress resistance of tomato plants than the treatment of Se or hormone alone. Among them, the combined application of Se and SA had the best effect on alleviating the cold stress of tomato plants compared with the ComCat ® (a commercial compound plant growth regulator). The co-application of Se and SA also prevented the oxidative damage caused by cold stress on tomato plant chloroplasts and preserved the plasma membrane integrity, as shown by an obvious decrease in MDA, H 2 O 2 , and O 2 −. levels during cold stress. The Se/SA treatment could also reduce the content of reducing sugar, sucrose, total soluble sugar, and starch accumulation caused by cold stress through the regulation of osmotic substances, so a