Question

In angiosperm the following events occurs during secondary growth. Arrange these events in correct sequence :

(a)Formation of secondary xylem and secondary phloem
(b)Dedifferentiation in primary medullary ray
(c)Formation of cork and secondary cortex
(d)Formation of vascular cambium

• A. b, d, c, a
• B. d, c, a, b
• C. d, b, a, c
• D. b, d, a, c

Answer 1

The correct option is D b, d, a, c

The formation of secondary vascular tissues from the cambium is a characteristic feature of dicotyledons and gymnosperms.

The process of formation of secondary tissues due to activity of vascular cambium and cork cambium for increasing thickness or girth or diameter of plant is termed as secondary growth.

On the basis of the activities of vascular cambium and cork cambium, the process of secondary growth can be discussed under the following headings:

• Activity of the vascular cambium
• Activity of the cork-cambium

During secondary growth, some cells of medullary rays become active and show meristematic activity, which form a strip of cambium in between vascular bundles, called inter-fascicular cambium.

Both the intra-fascicular and inter-fascicular cambium unite to form a complete ring called the cambium ring. The activity of the cambium ring gives rise to secondary growth.

A cambial cell divides into two daughter cells, one of which remains meristematic and other differentiates into secondary vascular tissue.

Phellogen or cork cambium develops in stems and roots of most dicots and a few monocots. It arises in the cortex or phloem tissue in stems, and from pericycle in roots. Cells formed on the outer side differentiate into cork cells (phellem cells) and cells cut off on inner side form the secondary cortex or phelloderm.

So, thev correct answer is "option C"