Effects of calcium application on activities of membrane transporters in Panax notoginseng under cadmium stress.

Pot experiments were conducted to study combined effects of Ca and Cd on contents of Cd and Ca, and membrane transporters activities (CC (calcium channel protein), ATPase and CAXs (cationic/H+ antiporter) of two-year old Panax notoginseng with application of different concentrations of Ca2+ (0, 180 and 360 mgkg-1, prepared by Ca(OH)2 and CaCl2, respectively) under Cd2+ (0, 0.6, 6.0, and 12.0 mgkg-1, prepared by CdCl2•2.5H2O) treatments. The results showed that soil available Cd contents decreased with Ca(OH)2 and CaCl2 application. Soil pH value increased with Ca(OH)2 application. The contents of Cd in all parts of P. notoginseng increased with the increase in Cd treatment concentrations. The Cd content of P. notoginseng decreased with Ca(OH)2 and CaCl2 treatments. The activities of CC and ATPase in the main root of P. notoginseng decreased with the increase in Cd treatment concentrations and application of CaCl2. The activities of CC and ATPase increased with Ca(OH)2application. The activity of CAXs in the main root of P. notoginseng increased with the increase of Cd treatment concentration. The results indicate that Ca and Cd should be both related to membrane transporters activities and activities of CC, ATPase and CAXs are promoted by cooperation of Ca2+and OH+, which suggest the Ca(OH)2 application should be better than application of CaCl2 for Cd detoxification.