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A Handbook of Biology

These are made up of sclerenchymatous cells. Generally

absent in primary phloem but are found in the secondary

phloem. These are much elongated, unbranched and

have pointed, needle like apices. Cell wall is quite thick. At

maturity, these fibres lose their protoplasm and become

dead. Phloem fibres of jute, flax and hemp are used

commercially.

Function: Mechanical support & protection to soft tissues.

PHLOEM FIBRES (BAST FIBRES)

THË TÏSSÜË SÝSTËM

Based on structure and location, tissue systems are of 3 types:

TISSUE

SYSTEM

Epidermal tissue system

Ground (fundamental) tissue system

Vascular (conducting) tissue system

ËPÏDËRMÅL TÏSSÜË SÝSTËM

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It forms the outer-most covering of the whole plant body.

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It comprises epidermal cells, stomata and epidermal appendages

(trichomes & hairs).

a. Epidermis

3

2

1

It is the outermost layer of the primary plant body.

Epidermis is usually single layered.

It is made up of elongated, compactly arranged parenchymatous cells

with a small amount of cytoplasm lining the cell wall and a large vacuole.