Metabolomics analysis to characterize the effects of flavonoids on tobacco seedlings under cold and hypoxia stress

Cold and hypoxia (CH) stress, a common combined stress during floating system, inhibits growth of tobacco and seriously affects the quality. Exogenous substances can regulate plant growth and respond to environmental stress. However, there are few studies focusing on tobacco responses to CH stress and the effects of exogenous substances on tobacco seedlings under CH stress are not fully understood. In this study, metabolomics analysis was performed on two tobacco varieties with contrasting CH responses, i.e. K326 (CH-sensitive) and Honghua (CH-tolerant). The results showed that flavonoids were crucial for tobacco seedlings to resist CH stress. Furthermore, exogenous anthocyanidin, flavone and quercetin significantly increased the root length, relative chlorophyll content, SP content, SOD, POD, CAT and APX activities of tobacco under CH stress, while reducing MDA content. Overall, our study highlighted the potential of flavonoids to improve CH tolerance of tobacco which could become a useful tool to resist stress during tobacco floating system.