Mass Propagation of an epiphytic orchid Acampe papillosa (Lindl.) through in vitro seed germination

Abstract

A method of in vitro propagation of a medicinally important epiphytic orchid of NBU campus Acampe papillosa has been developed. Three different categories of media (1/2 MS, MS and Knudson C) were used for in vitro asymbiotic seed germination for conservation and commercial uses. Seed germination was observed in all the media without any growth supplement or additives although not efficiently. Seeds showed positive germination response in all the three media but the frequency and onset of germination, protocorm formation and associated morphogenic changes leading to plantlets establishment varied with the nature of additional growth stimulus. Different concentrations and combinations of auxin and cytokinins were used to enhance the germination and seedling development. The different concentration of coconut water (CW) was used as additive supplement in this study and 15% CW showed good germination within 22 days in KnC medium. Various concentrations and combinations of plant growth regulators BAP (1mg l-1 to 4 mg l-1), NAA (0.5 mg l-1 to 2 mg l-1) and IBA (0.5 mg l-1 to 2 mg l-1) were added into the three categories of media as growth stimulants. The induction of PLBs was observed in the absence of any exogenous supply of PGRs, but the addition of BAP (4 mg l-1) with KnC medium improved the shoot growth significantly and enhanced the PLBs development (95% efficiency) with highest shoot length (2.5 cm) after six months of culture. Minimum number of days was required for seedling development (148 days) when cultured into the KnC medium supplement with combinations of BAP (4 mg l-1) and IBA (2 mg l-1). Addition of small quantity of NAA (0.5 mg l-1to 2 mg l-1) was not improved the PLBs or seedling development in compared to BAP and IBA. Rooting was improved by addition of IBA (0.5 mg l-1 to 2 mg l-1) into the media. High rate of rooting efficiency was recorded when combinations of auxin and cytokinin was used. Frequency of rooting (95%) was studied in KnC medium containing BAP (4 mg l-1) and IBA (2 mg l-1). Seedling of 2.5 cm long with 3-4 leaves were transferred to earthen pot containing wood charcoal and coco peat for acclimatization under green house conditions. Hardened plantlets showed significantly high survival rate (81%) after seven months of transfer. Therefore, the present method of micro-propagation could be used successfully to propagate this important orchid for commercial production and conservation purposes.