What is the part of the plant used in tissue culture called?

In tissue culture experiments using tobacco callus,it was observed that when the culture medium contains $2 \ ppm$ of $IAA$ and $2 \ ppm$ of kinetin,an undifferentiated mass of callus is produced. If the ratio of kinetin to $IAA$ is increased,what will happen?

In tissue culture,roots can be induced by

Murashige and Skoog's medium is used for

How is a somatic hybrid different from a hybrid?

Which auxin is commonly used in both callus and suspension cultures?