Evaluation of thermal-stress on the accumulation of podophyllotoxin in shoot in vitro cultures of Linum persicum

Linum persicum is an endangered plant native to Iran, from Linaceae family. Phytochemical analysis has shown that L. persicum in vitro cultures contain podophyllotoxin (PTOX), the pharmacological precursor for anticancer drugs such as etoposide, etopophos, and teniposide. Shoot culture of L. persicum was established from callus cultures in MS medium containing GA3. A study was designed to investigate the effects of thermal-stress treatments (TST) on the shoot growth pattern of L. persicum along with the accumulation of PTOX. Shoots were heat-stressed at 37, 40, 45, 50, and 55 °C for 3 h, and then transferred back to the growth room. In each thermal group after 2, 3, and 4 weeks, 4 flasks were extracted for PTOX analysis. HPLC analysis (