Question

When secondary growth is initiated in a dicot root, which of the following happens first?

• A. Cambial initials between xylem and phloem will divide.
• B. Pericycle strands, outside the primary xylem will divide.
• C. Periclinal division takes place, so that the cambium becomes circular.
• D. Parenchymatous cells between xylem and phloem become meristematic.

Answer 1

The correct option is D Parenchymatous cells between xylem and phloem become meristematic.

The parenchyma cells present between xylem and phloem elements in the vascular bundles constitute conjunctive tissue. The parenchymatous cells present beneath phloem take on meristematic activity and then divide to form cambial strands. This is followed by periclinal division of the cells of pericycle present against protoxylem to form multiple layers of cells, which are joined by cambial cells derived from conjunctive tissues and together they make a complete cambium ring. Thus, the correct answer is option D.