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A Handbook of Biology

VÅSÇÜLÅR ÇÅMBÏÜM

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It is the meristematic layer responsible for

cutting off vascular tissues (xylem and phloem).

(NEET 2018)

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In the young stem, it is present in patches as a

single layer between xylem & phloem. Later it

forms a complete ring.

Formation of cambial ring

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In dicot stems, cells of cambium present

between primary xylem & primary phloem is intrafascicular cambium.

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Cells of medullary cells, adjoining this intrafascicular cambium become

meristematic and form interfascicular cambium. (NEET 2013) Thus, a

continuous ring of cambium is formed.

Activity of the cambial ring

The cambial ring becomes active and begins to cut off new cells, both

towards the inner and outer sides. The cells that cut off towards pith, mature

into secondary xylem (NEET 2017). The cells that cut off towards periphery,

mature into secondary phloem.

Medullary

rays

Phellogen

Phellem

Epidermis

Cortex

Primary

phloem

Vascular

cambium

Primary xylem

Pith

Interfascicular cambium

Secondary

xylem

Secondary

phloem

Cambium

ring

Stages of Secondary growth in a dicot stem