Exogenous CaCl2 promoted the indole alkaloid accumulation in seedlings of Catharanthus roseus under NaCl stress

A sandy culture experiment was conducted to investigate the effects of exogenous CaCl2 on the indole alkaloid accumulation in Catharanthus roseus under salt stress. One-month seedlings of C. roseus were treated with the different concentrations of NaCl (0, 50, and 100mmoll(-1)) and 7.5mmoll(-1) CaCl2. The plant samples were analyzed after 7 days of the treatments. The NaCl-stressed plants showed decrease of fresh and dry weight and increase of malondialdehyde (MDA) content compared to control. Tryptophan decarboxylase (TDC) activity increased significantly under 50mmoll(-1) NaCl without CaCl2 addition, 50mmoll(-1) NaCl with 7.5mmoll(-1) CaCl2, and CaCl2 treatment without NaCl addition. There was a significant increase in peroxidase activity under NaCl stress compared to control. The vindoline, catharanthine, vincristine, and vinblastine contents increased under salt stress (especially with 50mmoll(-1) NaCl treatment with or without CaCl2). Addition of CaCl2 to NaCl-stressed plants increased biomass, TDC activity, vindoline, and catharanthine contents and lowered MDA and vincirstine contents compared to the plants without CaCl2. The plants treated with CaCl2 alone showed higher TDC activity, vindoline, catharanthine, and vinblastine content when compared to control. The results showed that exogenous CaCl2 could promote the indole alkaloid metabolism under salt stress.