Abstract: This work aims to study how the high temperature stress affects the cell vitality, the activity of defense enzyme and the contents of total triterpenoid in the suspension culture cells of birch, and determine the optimal heat stress treatment by which birch cells can be induced to synthesize triterpenoid. We set temperature of 35℃, 40℃, 45℃, 50℃ and 55℃ treating birch cells for 1, 2 and 4 h respectively, then measured the cells’ vitalities, the activities of defense enzymes’(SOD, CAT and PAL), and the contents of total triterpenoid. Under the treatments of 45-55℃, cell's vitality reduced significantly, and at 50℃ for 2 h was only 6.8% of the control group；meanwhile, the activities of SOD and PAL increased significantly and reached the highest while treated at 55℃ for 4 h and measured at 24 h, i.e., they increased 164.9% and 159.6% compared to the control group. However, the CAT activity was strongly inhibited, in lowest while treated at 55℃ for 2 h and 4 h and measured at 12 h. When treated at 50℃ for 2 h and sampled at 24 h, the contents of total triterpenoid were the highest with 76.66 mg/g, increased 105.6% compared to the control. Finally, we determined that the condition of treatment at 50℃ for 2 h and measured after 24 h was the optimal to induce the birch suspension cells to produce the triterpenoid.

Key words: birch, defense enzyme, triterpenoid, temperature stress birch, defense