Question

Extrastellar secondary growth occurs due to the activity of

• A. Intrafascicular cambium
• B. Interfascicular cambium
• C. Vascular cambium
• D. Cork cambium

Answer 1

The correct option is D Cork cambium

Intrafascicular 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, due to absence of pith rays dicot root lack it. Thus inter and intra fascicular cambium together forms a complete cambium ring, called as 'vascular cambium'.

Vascular cambium exhibits two patterns of division; multiplicative divisions or additive divisions, thus cut more actively at centre. Multiplicative divisions increase the circumference of the vascular cambium. Additive division adds phloem/xylem mother cell that differentiates into their respective cell types. The cells that cut off to outside are converted into secondary phloem tissues, while those towards centre produce secondary xylem, thereby causing slatellar growth.

The secondary growth in dicot stem occurs by the activity of cambium at the stellar region and cork cambium at the extra stellar region

So, the correct answer is 'Cork cambium'