Page 19 - E-Biology Sec.2 2024-2025 U1_Handy

1- Upper and lower epidermis:

Each consists of 1 layer of adjacent barrel parenchyma cells with no chlorophyll.
Their external wall is coated by cutin except the stomata. “more in lower”

2- Mesophyll tissue:

It lies between the 2 epidermis and is transversed by veins, it consists of:

Palisade layer Spongy layer

Perpendicular to the surface of upper Below the palisade.
epidermis.

1 row of cylindrical & elongated Irregular and loosely arranged
parenchyma. parenchyma with wide intercellular

It has many chloroplasts in the upper part spaces.
to absorb the largest amount of light.
It contains lower no. of chloroplasts than
palisade.

3- Vascular tissue:

It consists of vascular bundles extend in the veins and venules, the main bundle
is in the midrib and it consists of:
Xylem vessels: Vertical rows are separated by xylem parenchyma cells.

Phloem: It follows the xylem toward the lower surface of the leaf.
It translocates the organic food
that’re formed in the mesophyll

Organic food

to diff. parts of the plant.

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First Term