Ionic compositions play an important role on in vitro propagation of PLBs of spring-flowering Calanthe

Abstract

The effect of ionic composition in medium on proliferation of shoot tip-derived PLBs of two Calanthe species, C. aristulifera and C. striata, was investigated by using the media with 12 different ionic compositions, which were systematically modified according to the method of Ichihashi (1992) based on the composition of modified Gamborg’s B5 medium. These two species showed almost the same growth response to the ionic compositions and the growth of PLBs was inhibited on media with higher ratios of NH₄⁺ and Ca²⁺, but promoted with higher ratios of both K⁺ and H₂PO₄⁻. Based on the results of PLB growth, optimum cationic compositions calculated for C. aristulifera and C. striata were NH₄⁺ : K⁺ : Ca²⁺ : Mg²⁺=10.4 : 70.0 : 9.6 : 10.0 and 10.9 : 68.1 : 11.0 : 10.0, respectively, whereas optimum anionic compositions were NO₃⁻ : H₂PO₄⁻ : SO₄²⁻=42.1 : 43.7 : 14.2 and 43.0 : 42.9 : 14.1, respectively. The percentages of NO₃⁻ and H₂PO₄⁻ in the optimum medium thus obtained were about half and 12-hold of the control B5 medium, respectively. Among the 100 micropropagated C. striata plants examined, no obvious variation in flower shape and color were observed except two plants which had larger and thicker flowers than original plants. Those two variants were confirmed to be chromosome doubled tetraploids by flow cytometric analysis.