In vitro propagation of Platycerium bifurcatum (Cav.) C. Chr. via green globular body initiation

This study describes a Platycerium bifurcatum (Cav.) C. Chr. propagation method through initiation of green globular bodies (GGBs) from juvenile leaf explants of in vitro grown sporophytes. The GGB initiation was first obtained by incubating the explants on MS medium supplemented with α-naphthalene acetic acid (NAA) and two other cytokinins, 2-isopentenyl adenine (2ip) or 6-benzylaminopruine (BA). NAA at 5.37 μM was determined a better concentration for the initiation. However, as the cytokinin concentration in the medium increased, it inhibited GGB production. Individually harvested GGBs proliferated well on a medium supplemented with 5.37 μM NAA and 2.22 μM 2ip; they displayed less sporophyte formation but a faster increase in diameter. Multiple sporophytes were subsequently regenerated by culturing GGBs on a hormone-free MS medium at the regeneration stage. Non-rooted and separated sporophytes were directly transplanted to four different types of potting media, namely sphagnum, vermiculite, peat, and a mixed medium (vermiculite:peat = 1:1). Spontaneous rooting was observed during the first 4-week acclimatization period. Even with the omission of an adventitious root induction step, the survival rate of the plants was 88% or higher. No significant difference in plant survival was detected among the different media. Using our proposed propagation procedures, it was possible to obtain an estimated production of about 170 sporophytes per initial leaf explant (proximal section; 1/2 of the leaf ≤ 2.0 cm in length) during a 32-week culturing period.