Morphogenetic changes are induced by CK in presence of 

The ratio of auxin to cytokinin plays an important role in the effect of cytokinin on plant growth. Cytokinins are involved in many plant processes, including cell division and shoot and root morphogenesis. According to the "direct inhibition hypothesis," these effects result from the cytokinin to auxin ratio. Mature plant cells normally stop dividing. By adding cytokinin and auxin, differentiated cells can be induced to initiate cell division again. So, the correct option is 'IAA'.