This study aimed to evaluate effects of types and concentrations of plant growth regulators in a halfstrength Murashige and Skoog medium on somatic embryogenesis from protocorm-like bodies (PLBs) and
leaf segments of Dendrobium Sonia ‘Earsakul’ cultured for 8 weeks. It was found that media containing
thidiazuron (TDZ) either at 0.1, 0.3 and 1.0 mg/L alone or in combinations with 0.1 mg/L naphthaleneacetic
acid (NAA) or 1.0 mg/L 2,4-dichlorophenoxyacetic acid (2,4-D) provided no significant differences in
percentage of somatic embryogenesis (38.18-49%) from PLBs. Half strength MS supplemented with TDZ
either at 1 and 3 mg/L alone or combination with 0.1 mg/L NAA provided higher percentage of somatic
embryo formation and number of somatic embryo per explant more than supplemented with 0.1 mg/L NAA
alone. Low percentage of somatic embryogenesis was found from leaf segments. Leaf explants with the
dorsal surface in contact with a medium provided higher somatic embryogenesis (0-18.75%) than those
obtained from the explants with the ventral surface contact with culture medium (0.89-8.04%). Furthermore,
basal segments of leaves with ventral surface in contact with a medium showed higher somatic embryogenesis
and number of embryos (1.79-16.07% and 0.2-0.85, respectively) than those obtained from apical segments
(0-1.78% and 0-0.3, respectively). There was a significant difference in somatic embryogenesis (0-18.75%)
of a leaf when a dorsal surface was placed on the culture medium.