Question

Discuss the role of cambium in the secondary growth of dicot stems.

Answer 1

The secondary growth of dicot stems refers to the increase in the diameter of the plant. Cambium is a plant tissue layer found between xylem and phloem. Cambium plays an important role in increasing the girth of the stem in the stellar zone.

Complete answer:
Secondary growth in Dicot stems –
In the stellar zone: The first stage is the formation of the cambium ring by the fusion of the fascicular and the interfascicular cambium. The cambium ring is fifty percent primary and fifty percent secondary in origin. The second step is the activity of the cambium ring. The cells of the cambium ring produce new cells both inside and outside. The cells that are produced inside form the secondary xylem and the cells that are produced outside are known as the secondary phloem. The amount of the secondary xylem and the secondary phloem is initially the same but later on, the secondary xylem becomes much more than the secondary phloem. This is because the formation of the new cells on the inner side is much more than the formation of the new cells on the outer side. The secondary xylem formed inside crushes the primary xylem, finally exerting pressure on the cambium ring. The cambium ring then shifts outwards gradually and the amount of secondary xylem increases gradually. This leads to an increase in the girth of the stem.

Note: The secondary growth is defined as the growth which takes place in the later stages of development of the pant by the activity of the secondary meristems known as the cambium and cork cambium. This leads to an increase in the diameter of the plant which is known as secondary growth.