Ethylene was Involved in Ca2+-Regulated Na+Homeostasis, Na+Transport and Cell Ultrastructure During Adventitious Rooting in Cucumber Explants Under Salt Stress

Salt stress as one of main abiotic stresses damaged plant growth and development. In this study, the effects of ethylene on Ca2+-regulated rooting index, Na(+)and K(+)concentration, Na(+)transportation and cell ultrastructure during adventitious rooting in cucumber (Cucumis sativusL.) under salt stress were investigated. The results showed that ethylene might play a positive role in Ca2+-regulated rooting index during adventitious rooting under salt stress. Moreover, CaCl(2)treatment significantly decreased the intracellular Na(+)level but increased K(+)content of cucumber explants under salt stress. However, the Na(+)and K(+)concentration which treated with Ca(2+)treatment was significantly influenced by ethylene inhibitors under salt stress. Our results also showed that ethylene might be involved in Ca2+-affected cell ultrastructure of cucumber explants under salt condition. Further analysis showed that ethylene might be responsible for Ca2+-regulated Na(+)transport through enhancing the transcriptional and protein levels of Na+/H(+)antiporter as well as H+-ATPase for alleviating the negative effects of NaCl stress. Therefore, ethylene might act as a downstream signaling molecule of Ca(2+)to maintain Na(+)and K(+)homeostasis via regulating Na(+)transport and preserve the integrity of cellular ultrastructure of cucumber explant during adventitious rooting under salt condition.