THE EFFECT OF CYTOKININ TYPE AND CONCENTRATION AND THE NUMBER OF SUBCULTURES ON THE MULTIPLICATION RATE OF SOME DECORATIVE PLANTS

Long-term micropropagation of some plants by tissue culture was investigated. The plants studied can be divided into three groups according to their sensitivity to cytokinins benzyladenine (BA) and kinetin (K). (1) Plants (gerbera cultivars) whose multiplication on BA media is not recommended. Permanent high K level must also be avoided. It must be decreased gradually during a long-term culture. After the 8th or 9th subculture the shoots are to be transferred to the resting medium with 0.1 mg/L K and 1.0 mg/L indoleacetic acid. (2) Plants ( Cordyline, Dracaena, Dieffenbachia) that may be multiplied on media containing either BA or K, the latter being preferable as its concentration may be varied within a larger range (0.5-4 mg/L) without negative side effects. (3) Plants ( Philodendron, Spathiphyllum, Musa) that may be multiplied on BA media without even relatively high BA concentrations (5 mg/L) leading to vitrification. However, in order to obtain the best shoots for rooting, the BA content of the multiplication media has to be reduced to 1/2-1/3 of its original value after the 5th or 6th subculture.