Correct answer: Meristem
A meristematic tissue is a type of tissue that contains the unspecialized stem cells, which divide to give cells that increase the height of the plant, girth of the stem, and roots of the plant. They also give cells that form flowers and leaves.
To perform all these functions, a meristematic tissue produces daughter cells that are known to differentiate into organ, whole plant or the whole genome of the plant.
Example: Apical meristem, lateral meristem etc