State whether the following statements are true or false.
An undifferentiated plant callus in tissue culture is stimulated to differentiate by the relative amounts of auxin and cytokinin present.

The correct option is A True
A differentiated callus is dependent upon the concentration and ration of auxin and cytokinin. Auxin is the growth hormone that promotes the elongation and growth of root tissues while cytokinins are the opposite of auxins, they will be in higher concentration at the time of shoot formation. Thus, both the hormones have their respective functions and roles regarding the growth of the plant. The callus is differentiated only when both auxin and cytokinin are present, in the absence of any one of these hormone callus division will not occur. Both hormones should be present in a proportionate amount, in plants auxin is generally present which is responsible for roots. These roots later produce cytokinin which helps in the formation of shoots.

So, the correct statement is 'True'.