In vitro propagation of the endangered tree fern Cibotium barometz through formation of green globular bodies

Cibotium barometz is an endangered tree fern, used both as ornamental plant and traditional Chinese medicinal plant. In this study, an effective in vitro propagation protocol was obtained through formation of green globular bodies (GGBs) from in vitro juvenile sporophytes. The effect of plant growth regulators (PGRs) on GGB induction and multiplication, as well as mineral salt concentration and active charcoal (AC) on plantlet regeneration from GGBs was evaluated. Thidiazuron (TDZ; 1-phenyl-3-(1,2,3-thiadiazol-5-yl) urea) had a significant effect on GGB induction and multiplication ( P < 0.001), while a-naphthaleneacetic acid (NAA) did not ( P > 0.05). GGB induction rate was above 80 % on 1/2 Murashige and Skoog (MS) media supplemented with TDZ (1.0 mg L − 1 ) and NAA (0.1, 0.3 or 0.5 mg L − 1 ). The same media were also optimal for GGB multiplication. GGBs cultured on 1/4 MS media supplemented with 0.1 or 0.2 % (w/v) AC showed a high rate of GGB development into plantlets above 90 %. 1/2 MS media supplemented with 0.1 or 0.2 % AC were the most effective for plantlet growth. Regenerated plantlets were successfully acclimatized (80 %) in greenhouse conditions. Morphological and histological analysis revealed that C. barometz GGBs was a yellow-green globular structure composed of the single GGB with meristems and hair-like structures, and new single GGBs were initiated from the epidermal cells of meristem zone.