GALL FORMATION IN CROFTON WEED - DIFFERENCES BETWEEN NORMAL STEM TISSUE AND GALL TISSUE WITH RESPECT TO CYTOKININ LEVELS AND REQUIREMENTS FOR INVITRO CULTURE

The tissue from galls induced by the gall fly Procecidochares utilis on the stems of Ageratina adenophora did not require the addition of cytokinins to the medium in order to survive and produce callus. This callus also produced 'hairy roots' in culture. Neither of these characteristics were shown by tissue from normal stems. It would appear as if the gall tissue was habituated with respect to its cytokinin requirement. When cytokinin was applied to the gall callus for a period of time, it lost its ability to grow on a cytokinin-free medium. Gall tissue contained much higher levels of endogenous cytokinin than normal stem tissue.