Question

A student cultures a callus from the tobacco pith in a sterilised minimal nutritive medium but adds more cytokinins than auxins. What would develop first from callus - shoot, buds or the roots?

Answer 1

The callus consists of undifferentiated tumor like cells. If the concentration of auxin with respect to that of cytokinin ratio is changed, the cells of the callus undergo transformation to produce organs like roots or shoots. If the level of cytokinin is high as compared to the auxin level, the callus cells undergo transformation and produces shoots.

High concentrations of cytokinin generally inhibit or delay root formation and also prevent root growth. High levels of cytokinin usually causes many small shoots to be produced.

Hence, shoot would develop first from the callus.