Response of Chelidonium majus in vitro cultures and their alkaloid content under heavy metal stress

Heavy metal contamination is becoming an increasing environmental problem worldwide. Heavy metals (HM) retard plant growth, yield and affect the secondary metabolism which results in fluctuations in plant metabolites, such as the alkaloids. The aim of the study was to investigate the influence of HM on the growth of in vitro cultivated plants of Chelidonium majus and their alkaloid content. The plants were cultivated on a medium B5 with double the amount of macrosalts, 0.5 g/l activated charcoal and supplemented with different concentrations of HM – Cd²⁺ (0.5; 1 mg/l); Pb²⁺ (100; 250 mg/l); Zn²⁺ (100; 250 mg/l). Plants were obtained in vitro from seeds or were propagated through adventitious shooting (AS). The raw alkaloid mixtures (RAM) were obtained by usual chemical procedure.
Plants cultivated at the lower concentration of Cd²⁺ formed roots and developed normally with a gradual reduction in their growth and rooting as the concentration of the supplemented HM increased. There were not any differences in the development of the plants cultivated on Cd²⁺ according to their type of origin. Epinasty and browning of the leaves were observed among the plants cultivated on the medium supplemented with Pb²⁺. These side effects got worse as the concentration of the HM increased, and were also accompanied by a strong reduction in the rooting. The plants which were obtained from seeds developed normally and did not show any of the signs of the ones which were propagated through AS. None of the plants cultivated on a medium supplemented with Zn²⁺ survived, regardless of their origin and HM concentration. A phytochemical study showed that the plants cultivated at the highest concentrations of Cd²⁺  and Pb²⁺  and also obtained through AS had the highest RAM. However, the plants cultivated at the same concentrations but obtained from seeds had lower RAM similar to that of the plants cultivated at lower concentrations of HM and propagated through AS.
In conclusion, Ch. majus was able to cope with the influence of Cd²⁺  and Pb²⁺  in the culture medium, but not with that of Zn²⁺. Quantity of RAM was influenced by the HM concentration and the origin of the plants.