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Rhizome mediated in vitro propagation of Geodorum densiflorum (Lam.) Schltr. was performed, using two- and half-month-old protocorms developed on a modified version of Murashige and Skoog [Physiol. Plant. 15 (1962) 473] medium, supplemented with various organic substances and plant growth regulators. In the control less than 50% of the protocorms formed rhizomes, but considerable enhancement was achieved with the application of both N6-benzylaminopurine (BAP) and α-naphthalene acetic acid (NAA). On the basis of morphology and growth habit, two types of rhizomes were obtained. The presence or absence of BAP in the culture medium was the determining factor for the induction of these morpho types. In the control and in the presence of NAA alone the movement of rhizomes was always positive orthogravitropic, but the application of higher concentration of BAP favoured diagravitropic movement. In general, growth and axillary branching of the rhizomes were best in the presence of NAA, whereas BAP promoted shoot formation. However, shoot formation was also noted in the absence of BAP, for which attainment of a critical rhizome length was essential. Swelling of the newly developed shoot to form a pseudobulb, followed by rooting was spontaneous in most cases, but the presence of BAP proved inhibitory. A preliminary planting trial of the seedlings in the natural habitat resulted in 60% survival rate. |
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