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Two Phalaenopsis orchids, Phalaenopsis amabilis and Phalaenopsis ‘Nebula’, were used to test the effects of induction period (30, 45 and 60 days), subculture period (30, 45 and 60 days), and explant length (1, 1.5 and 2 cm) on direct somatic embryogenesis from different regions (leaf tip, adaxial side, abaxial side and cut end) of leaf explants from in vitro grown seedlings. The results showed that the cut end had a highest competence to form embryos than the other regions of the leaf explants from both orchids. In addition, the suitable culture conditions were 60 days for induction period in darkness, 45 days for subculture period in light and 1 cm for explant length. Besides, the combinations of N6-benzyladenine (BA) and naphthaleneacetic acid were tested on their effects on plantlet conversion and further development of leaf-derived embryo. It was found that 0.5 mg/l of BA showed the highest response on plantlet conversion rate and the lowest browning rate of explants. In this communication, the embryo structures and development were proved by scanning electron microscopy. [ABSTRACT FROM AUTHOR]

The influence of light regime, explant position and orientation on direct embryo formation from leaf explants of two Phalaenopsis, P. amabilis and P. Nebula, were investigated to optimize the protocol for regenerating of this orchid. When explants were cultured in light, direct embryogenesis was retarded in both species. Embryos showed whitish to pale green in color and larger size than those cultured in darkness. Furthermore, light regime induced explant browning, embryo necrosis and eventually low plantlet conversion rate. Sixty days of culture in darkness is the most suitable duration for direct embryo induction. Explant orientation also significantly affected direct embryo formation, and explants placed adaxial-side-up on culture medium had higher embryogenic response than abaxial-side-up orientation. In both species, the cut end had highest embryogenic competence than other parts of the explant. Moreover, when the leaf explant was cut transversely into two segments, the leaf basal segment had higher embryogenic competence than the leaf tip segment. [ABSTRACT FROM AUTHOR]

Leaf explants of two Phalaenopsis, P. amabilis and P. Nebula, were used to test the effects of auxins (2,4-D, IAA, IBA, NAA), cytokinins (2iP, BA, kinetin, TDZ, zeatin), GA3, ancymidol, polyamines (putrescine, spermine, spermidine), ACC, AgNO3 and CoCl2 on the amount of direct embryo formation on different leaf locations (the cut end, the adaxial side, the abaxial side and the leaf tip). The results showed that there was a genotypic effect on direct embryo formation induced by cytokinins that 13.32 μM BA and 4.92 μM 2iP was the most effective in P. amabilis and P. Nebula, respectively. Besides, explant position highly affected embryogenic competence of leaf cells in both species that the cut end showed highest embryogenic response, the adaxial side was the second, and then the abaxial side and the leaf tip. Altogether, cytokinins tested were all effective in both species, and ACC at 20 μM had 35% of embryogenic response in P. amabilis. However, auxins, GA3, ancymidol and polyamines were inhibitory in both species. [ABSTRACT FROM AUTHOR]