Optimizing callus formation in the endangered medicinal tree Hydnocarpus macrocarpa using phytohormone

Abstract

Hydnocarpus macrocarpa (Flacourtiaceae) is one of the endemic and endangered medicinal tree, was selected to investigate the influence of plant growth regulators on callus formation. H. macrocarpa is majorly distributed at low and medium elevations of the Southern Western Ghats. The seeds of this plant are used for the treatment of ulcers, biliousness, leprosy and epilepsy. An experiment was carried out with two different methods. In the first method Murashige and Skoog (MS) medium supplemented with cytokinin alone or combined with auxin (2–4-Dichlorophenoxy acetic acid; Naphthalene acetic acid; Indole acetic acid; Indole butyric acid and Gibberellic acid) at different concentrations (1, 2, 3, 4 and 5 µM) were used; in the seond method, MS medium supplemented with coconut endosperm (Solid and liquid) extract (1, 2, 3, 4 and 5 %) with Aloe vera jelly extract at different concentrations (1, 2, 3, 4 and 5 %) in combination and separately were used. Among the different treatments, good callus proliferation was obtained using MS medium supplemented with Benzylaminopurine and in combination with Naphthalene acetic acid and 2–4-Dichlorophenoxyacetic acid (3 µM and 4 µM). But the best callus proliferation, shoot tip proliferation; auxiliary root and shoot formation were observed in MS medium supplemented with Aloe vera jelly extract in combination with coconut endosperm extract. The natural growth regulators supplemented with the media gave a positive response for plant growth. The results showed that the natural growth regulators, such as coconut endosperm and Aloe vera jelly extracts were found to be more efficient than the synthetic growth regulators (auxin and cytokinin). The presence of Indole acetic acid and Indole butyric acid in both Aloe vera jelly extracts and coconut endosperm were confirmed by High performance liquid chromatography and Fourier transform infrared spectroscopy analysis.