Effects of Combinations of Growth Regulators, and of Organic Supplements on the Growth of Cattleya Plantlets Cultured in vitro

Cattleya plantlets about 5mm in height were subcultured on the basal medium supplemented with selected combinations of growth regulators and organic nutrient sources so as to find the culture medium most effective for in vitro propagation of Cattleya plantlets. The reuslts obtained are as follows:1) Some synergistic effects were recognized in each of the four selected combinations of growth regulators added to the basal medium. When combined with 2, 4-D, however, the other growth factors exerted stimulative effects on the plantlet development only within a narrow range of their concentrations.2) The development of Cattleya, like that of Cymbidium, was divided into four stages, i.e., protocorm formation, protocorm proliferation, shoot formation, and plantlet growth. The developing Cattleya seemed to require different media compositions that were specific to each stage of plant development.3) The culture media most effective for plantlet growth included 0.1 to 1.0mg/l kinetin and 1.0 to 5.0mg/l NAA or 0.1 to 0.5mg/l kinetin and 0.1mg/l 2, 4-D.4) Shoot formation of propagules was promoted most effectively by using culture media containing 6-benzyladenine at 1.0mg/l and NAA at 0.5mg/l or kinetin at 0.1mg/l and 2, 4-D at 0.1mg/l.5) Protocorm proliferation was stimulated most effectively by 5.0mg/l 6-benzyladenine and 0.1mg/l NAA which were added in combination to the basal medium.6) The culture media, containing kinetin at 0.1 to 5.0mg/l and 2, 4-D at 0.5mg/l or 6-benzyladenine at 0.5 to 5.0mg/l and 2, 4-D at 0.5 to 1.0mg/l, formed large numbers of protocorms around the apical and axillary meristems of the shoot. Relatively high concentrations of growth regulators induced the formation of protocorms or callus-like protocorms even at the root tip and on the leaf surface.7) With respect to organic supplements, banana juice stimulated the growth of plantlets while raw coconut milk promoted the shoot formation and protocorm proliferation of Cattleya.