Feeding elicitor: Eight-week-old in vitro Stemona
plantlets were cultured in liquid MS medium
supplemented with various concentrations of chitosan or
yeast extract for one and two weeks at concentrations of
25, 50, 100 and 200 mg/L. The control treatment was
cultured in liquid MS medium without adding any elicitor.
Yeast extract was dissolved in distilled water and chitosan
was dissolved in 1% acetic acid. All culture experiments
were performed in triplicate. Roots from all treatments, as
well as the cultured medium, were extracted and analyzed
for Stemona alkaloid production. The total Stemona
alkaloid production was expressed as the sum of the
amount of alkaloid in the root and medium.