Question

Secondary growth in dicot plants is mediated by
(a) Cork Cambium
(b) Vascular Cambium
(c) Wound Cambium
(d) Both A and B

Answer 1

Hint: Secondary growth is the formation of tissues from lateral meristems which increases the diameter of the stem. It occurs through the secondary meristems that are formed in stems and roots after the differentiation of primary plant tissues.

Complete answer:
The secondary meristems that are formed in stems and roots after the tissues of the primary plant body are differentiated include the vascular cambium and the cork cambium. The vascular cambium adds to the diameter of stems and roots by giving rise to woody tissues. The cork cambium gives rise to some of the bark of the trees.
Vascular cambium is formed by joining of the intrafascicular and interfascicular cambia. These cells divide in the periclinal fashion and give rise to the secondary vascular tissues and ray parenchyma. Cork cambium arises from the dedifferentiation of cortical tissues that are present in the cortex. These cells undergo periclinal divisions and produce cork towards its outer side and secondary cortex towards its inner direction.
The vascular cambium produces secondary xylem tissues on the inner side of the ring, and secondary phloem on the outside, which pushes the primary xylem and phloem apart, whereas the cork that is produced by the cork cambium functions as a thick layer of cells that performs the function of protecting the delicate vascular cambium and secondary phloem from mechanical damage, predation, and desiccation.
So, the answer is, “Both A and B”.

Note: Secondary growth is seen only in the dicots and is absent in the monocots. This is because the stele of the monocots is developed in such a way that they do not show the presence of cambium in the vascular bundle. Due to the absence of vascular cambium between xylem and phloem, no secondary growth is seen in the monocots.