Effects of calcium application on the yields of flavonoids and saponins in Panax notoginseng under cadmium stress

Abstract

ABSTRACT Under different concentrations of cadmium treatments (Cd2+ concentration: 0, 0.6, 6.0, 12.0 mg/kg, prepared with CdCl2•2.5H2O), pot experiments were conducted to study the application of two calcium-containing substances (Ca2+ concentration: 0, 180, 360 mg/kg, prepared with calcium chloride CaCl2 and lime Ca(OH)2) on the yields of flavonoids and saponins of P. notoginseng. The results showed that the application of calcium chloride and lime could increase the biomass of the main root of P. notoginseng and significantly reduce the cadmium contents. Under 0 and 0.6 mg/kg cadmium treatment, the cadmium content in the main root of P. notoginseng did not exceed the standard value (Cd≤0.5 mg/kg1, GB/T 19086–2008). Under 0.6 mg/kg cadmium treatment, the application of calcium chloride increased the yield of flavonoids in the main root of P. notoginseng. The yield of flavonoids in the main root of P. notoginseng decreased under the treatment of 360 mg/kg Ca2+ lime and 0.6 mg/kg Cd2+. Under the treatments of 6.0 mg/kg and 12.0 mg/kg cadmium stress, calcium chloride and lime reduced the yield of flavonoids in P. notoginseng by 14.2%-35.2%. There was a significant positive logarithmic function correlation between flavonoid yield and ratio of Ca/Cd treatment concentration (P < 0.05). Under the treatment of 0.6 mg/kg Cd2+ with 180 mg/kg Ca2+ (calcium chloride), yields of Rg1, Rb1 and total saponins of P. notoginseng reached the highest and were increased by 114.9%, 323.0% and 172.4%, respectively, compared with no calcium chloride treatment. Under different Cd treatment levels and lime application, the yields of Rg1, Rb1 and total saponins of P. notoginseng decreased and the yield of R1 remained relatively stable. Under a certain concentration of cadmium treatment, appropriate calcium chloride and lime application could increase or maintain the biomass, saponin and flavonoid yields of the main root of P. notoginseng. Yields of R1, Rg1, Rb1 and SPN were influenced due to interaction of Cd2+ and Ca2+. In order to ensure the cadmium content of P. notoginseng less than the standard value and optimal yields of flavonoids and saponins, it could be recommended to apply calcium chloride or lime 1125 kg/hm (180 mg/kg Ca2+) under 0.6 mg/kg Cd2+ treatment.