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

e e ect 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 di erent ionic compositions, which were systematically modi ed according to the method of Ichihashi (1992) based on the composition of modi ed Gamborg’s B5 medium. ese 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 − : SO4=42.1 : 43.7 : 14.2 and 43.0 : 42.9 : 14.1, respectively. e 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 ower shape and color were observed except two plants which had larger and thicker owers than original plants. ose two variants were con rmed to be chromosome doubled tetraploids by ow cytometric analysis.