Question

What is the secondary growth in stealer and extra stealer region in dicot stem

Answer 1

Answer:

A. In the Intra-Stelar Region:

The secondary growth always begins in the intra-stelar region. The meristematic cells of the cambium of the vascular bundles, called fascicular cambium, begin to divide and produce new cells on the outer and inner sides. Almost simultaneously a few paren­chymatous cells of the medullary rays become meristematic in a line with the fascicular cambium of the vascular bundle and join with the latter to form a complete cambium ring.

Newly formed strips are known as inter-fascicular cambium. A cambium cell divides into two cells, one of which remains meristematic, and the other one is modified either into a xylem element or a phloem element.

That is how the cambium perpetuates itself. The newly formed cells on the inner side are modified into secondary xylem elements, and those on the outer side into secondary phloem elements. Thus the primary xylem and phloem are gradually pushed apart from each other.

The cambium cylinder always produces more xylem than phloem; so the ring, with all the tissues in front of it, is pushed more and more towards the periphery.

Explanation:

Sometimes drought conditions prevail during the middle of a growing season resulting in formation of more than one annual ring. These are called pseudo annual rings. Secondary growth takes place in extra stelar region due to the activity of cork cambium. Cork cambium is also known as Phellogen or Extra stelar cambium.

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