The main problem associated with somatic embryo (SE) formation from mature plant explants is their low embryogenic competence. Kalopanax septemlobus (Thunb.) Koidz is a timber-yielding medicinal tree that is recalcitrant to somatic embryogenesis from explants derived from mature trees. In the present study, leaf explants derived from a 40-year-old K. septemlobus tree were subjected to osmotic stress, 2,4-D shock, chilling, or starvation stress to induce somatic embryogenesis. All of the stress treatments resulted in SE induction except control, the rates of which depended on the duration of the treatment. Maximum SE formation (23.3 %) was observed in explants treated with 1 M sucrose solution for 6 h, followed by explants treated with 100 lM 2,4-D for 1 day (16.7 %) while non-treated explants failed to produce somatic embryo. Callose accumulation from leaf explants after these two treatments increased 40- and 30-fold, respectively, compared with the control. Thus, osmotic stress produced by sucrose and 2,4-D shock treatment for a specific period of time can substantially increase the number of SEs formed from leaves from the grafted shoots of mature K. septemlobus trees. The results of this study may be useful for producing SEs from this valuable plant, as well as for breeding programs for improving selected K. septemlobus genotypes.
Financed by the National Centre for Research and Development under grant No. SP/I/1/77065/10 by the strategic scientific research and experimental development program:
SYNAT - “Interdisciplinary System for Interactive Scientific and Scientific-Technical Information”.