Effect of the plant growth regulators, α-naphthaleneacetic acid (NAA) and 6-benzylaminopurine (BAP), on protocorm organogenesis of Spathoglottis plicata Blume.

Abstract

Spathoglottis plicata Blume is known to be difficult to propagate by natural methods. The use of in vitro culture methods would result to a faster, more practical and more efficient means for its propagation. In this study, the appropriate concentrations of plant growth regulators (PGRs) on plantlet regeneration from Spa. plicata protocorms were investigated. Protocorms obtained from in vitro germinated seeds were cultured in halfstrength Murashige and Skoog (MS) basal medium with modified Nitsch & Nitsch (N&N) vitamins, 3% sucrose, 0.2% activated charcoal and 0.55% pharmaceutical agar. The culture medium was supplemented with α-naphthaleneacetic acid (NAA) and 6-benzylaminopurine (BAP) at different concentrations. The effects of NAA and BAP on protocorm cultures were evaluated based on their shoot length, number of leaves, root length and number of roots. Cultures responded positively to half-strength MS basal medium without PGRs based on their morphological characteristics. The maximum shoot length (29.87 ± 1.521 mm) was obtained at 0.5 mg/L BAP. It was generally observed that low concentrations of BAP, with little to no NAA, favored the elongation of shoots in culture. The number of leaves per plantlet was not significantly affected even with the addition of combinations of BAP and NAA. For root length, the highest obtained (16.40 ± 1.479 mm) were observed in media having 0.5 mg/L NAA and in 1.0 mg/L NAA and 0.5 mg/L BAP. Root length was observed to be high in cultures with low concentrations of NAA and BAP combinations. The greatest frequency of rooting (2.8 ± 0.175) was observed in media supplemented with only 2.0 g/L NAA. Medium containing predominantly NAA, with low concentrations of BAP, was observed to favor root formation in cultures.