Effects Of Salt Stress And Plant Growth Substance On The Growth And Indole Alkaloid Metabolism Of Catharanthus Roseus

Catharanthus roseus (L.) G. Don is a perennial, important medicinal and evergreen herb in the dogbane family (Apocynaceae). The terpenoid indole alkaloids (TIAs) in the plant’s composition such as catharanthine, vinblastine and vincristine are very important secondary metabolic productions owing to their wide pharmaceutical applications for human health.The metabolism and regulation of C. roseus alkaloids have been intensively investigated and that consequently the metabolizing ways were under coordinate regulations. Alkaloids are under organ-, development-and environment-specific and plant growth regulators control.In present study, the effects of different concentrations of NaCl and seawater stress, precursor, plant growth substance on the growth and alkaloid contents were determined to explicit relationship between alkaloid biosynthesis and environmental factors, moreover, provide useful data for enhancing the yield of the alkaloid by artificial cultivation. The main results obtained as follows.1. Seedlings of C. roseus were treated with different concentrations of NaCl (from0to250mmol·L-1) and seawater (from0to40%) stress respectively. Under salt stress, the fresh weight and dry weight of C. roseus seedlings decreased whereas the TBARS contents increased. The TDC activity was highest under50mmol-L"1NaCl stress, and then decreased with the increasing of NaCl concentrations. The vindoline, catharanthine, vinblastine and vincristine contents and yield of per plant were highest under50mmol·L-1NaCl treatment.The activity of TDC was highest with10%seawater treatment. The contents of vindoline and catharanthine were highest under10%stress compared with other treatments. And vinblastine contents increased with the increasing of seawater concentrations. Consequently, salt stress could restrain the growth of C. roseus seedlings, while promote the metabolite of alkaloid and enhance the alkaloid contents. Results from this experiment showed that under the salt treatment, the biomass of C. roseus seedlings decreased significantly, but the primary goal alkaloids yield were significantly higher than that of fresh water irrigated plants, especially in50mmol·L-1NaCl and10%seawater-treated plants.2. A sand culture experiment of C. roseus was conducted to determine the effects of different concentrations of NaCl (25and50mmol·L-1) and seawater (5%and10%) treatments on various durations of plant growth, inorganic ions and indole alkaloid concentrations in C. roseus. The salt-stressed plants had decreased the total fresh and dry weight and tissue K+concentration of C. roseus, and increased Na+and Cl-concentrations in roots, stems and leaves when compared to the control. The vindoline, catharanthine, vinblastine and vincristine concentrations and yield of per plant increased under seawater treatment. Under5%seawater and25mmol·L"1NaCl treatments, the concentrations and yield of the four kinds alkaloid were higher than that of10%seawater and50mmol·L-1NaCl treatments. Considering the industrial alkaloid production, it could reduce the cost of producing of alkaloid. In control plants, the highest of alkaloid concentrations were measured on100days after planting (DAP); hence, plant harvest must be optimized in terms of growth duration.3. Applied exogenous2.5and7.5mmol·L-1CaCl2had no effects on the growth of non-salt-stressed plants where as12.5mmol·L-1CaCl2decreased their biomass. TDC activity, vindoline, catharanthine and vinblastine contents and yield of per plant increased when exposed to exogenous CaCl2. Supplemental2.5and7.5mmol·L-1CaCl2had no effects on the vincritine content and yield while12.5mmol·L-1CaCl2treatment decreased the vincristine content and yield against control.Applied7.5mmol·L-1CaCl2to NaCl treated plants increased fresh and dry weight whilst decreased TBARS contents. TDC activity increased significantly under NaCl with or without CaCl2(7.5and12.5mmol·L-1) treatment when compared with the control. The vindoline, catharanthine, vincristine and vinblastine concentrations increased under salt stress. Exogenous7.5mmol·L-1CaCl2to100mmol·L-1NaCl-stressed plants increased indole alkaloid concentrations and yield of per plant significantly when compared with control. Exogenous CaCl2(7.5mmol·L-1) could promote the indole alkaloid metabolism under salt stress. 4. Exogenous tryptophan restrained the growth of non-salt-stressed C. roseus seedlings and promoted the alkaloid accumulation, but the yield of per plant had no significant change when compared with control. Supplemental100mg·L-1tryptophan alleviated the salt stress (100mmol·L-1NaCl) damage on the C. roseus seedlings and increased vindoline, vinblastine and vincristine yield of100mmol·L-1NaCl-stressed plant.5. Exogenous abscisic acid (ABA) decreased the biomass of C. roseus seedlings. The TDC activity increased significantly with50and100μmol·L-1ABA treatments against control. With ABA treatment, the vinblastine yield increased when compared with control. Exogenous ABA (10and5050μmol·L-1) could alleviate the effects of salt stress on the C. roseus seedlings. Applied ABA to100mmol·L-1NaCl-treated plants increased the contents and yield of vindoline, catharanthine, vinblastine and vincristine.Supplemental methyle jasmonate (MeJA) to non-salt-stressed plants reduced the biomass of the seedlings but enhanced the TDC activity and increased the alkaloid contents and yield. Applied exogenous MeJA (100μmol·L-1) alleviated the effects of salt stress on the C roseus seedlings. Supplemental200μmol·L-1MeJA to100mmol·L-1NaCl-treated plants increased the contents and yield of vindoline, catharanthine, vinblastine and vincristine. Compared with the ABA, MeJA was more preferable to promote the alkaloid metabolism of C. roseus seedlings.