Question

Growth rings are formed due to the activity of

• A. Intrastelar cambium
• B. Intercalary cambium
• C. Extrastelar cambium
• D. Primary cambium

Answer 1

The correct option is A Intrastelar cambium

Intrafascicular/intrastelar cambium is present between xylem and phloem in dicot stem and roots. Pith rays, present between the edges of intrafascicular cambium, divide to form a new cambium strip between the two vascular bundle i.e. interfascicular cambium. Thus, inter and intra fascicular cambium together forms a complete cambium ring, called as vascular cambium, which forms secondary xylem on inner side and secondary phloem on outer side. Differential cambial activity during autumn and spring season result in narrow and wide secondary xylem rings respectively, which together forms the annual growth ring.

Hence the correct option is A.