Describe the structure, functions and adaptation of the following parts of a leaf : (a) cuticle (b) epidermis (c) guard cells d) palisade mesophyll

Describe the structure, functions and adaptation of the following parts of a leaf :

i) cuticle
ii) epidermis
iii) guard cells
iv) palisade mesophyll
v) Spongy mesophyll layer
vi) Vascular bundle/tissue

Answers

i) Cuticle

This is the outermost layer of the leaf.
It is a thin non-cellular, Waxy, transparent and waterproof layers that coats the upper and lower leaf surfaces.

Functions of the cuticle

a) Being waterproof, it minimizes water loss from the leaf cells to the environment through transpiration and evaporation.

b) It protects the inner leaf tissues from mechanical damage.

c) It prevents entry of pathogenic microorganisms into the leaf.

ii) Epidermis

This is the outermost one cell thick layer covering upper and lower leaf surfaces. Its cells are ?attened and lack chloroplasts.

Functions of the epidermis:

a) It protects the leaf from mechanical damage.

b) It also protects the leaf from entry of disease-causing microorganisms.

c) It secretes the cuticle.

There are many small pores on the epidennis known as stomata (singular-stoma) through which exchange of materials occur. The opening and closing of the stomata is controlled by the guard cells. Each stoma is controlled by two guard cells.

iii) Guard cells

The guard cells have chloroplasts and are bean shaped. They have thicker inner cell wall and thinner outer cell wall.

Adaptations of the guard cells

•They have deferentially thicker walls to enable them bulge as they draw water through osmosis from the neighboring cells making them to open the stomata.
•They contain chloroplasts that manufacture sugars which increase osmotic pressure of the guard cells. As they draw water through osmosis, they bulge making the stomata to open.

iv) Palisade mesophyll

This is the chief photosynthetic tissue in plants. Its cells are regular in shape.
Its cells contain numerous chloroplasts for photosynthesis.
Their close packing and location just below the epidermis enables them to trap maximum sunlight for photosynthesis.
Location of palisade layer on the upper surface explains why upper leaf surfaces are greener than the lower surfaces.

v) Spongy mesophyll layer

This layer contains loosely arranged irregular cells. This leaves large airspaces between the cells which permits free circulation of gases carbon (IV) oxide and oxygen into the photosynthetic cells. Spongy mesophyll cells contain fewer chloroplasts compared to palisade cells.

vi) Vascular bundle/tissue

This is found in the midrib and leaf veins. Vascular bundle is made of phloem and xylem tissues. Xylem tissues conduct Water and some dissolved mineral salts from the roots to other plant parts while phloem translocates manufactured food materials from photosynthetic areas to other plant parts.

Anganifelix answered the question on May 8, 2018 at 16:11

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Describe the structure, functions and adaptation of the following parts of a leaf : (a) cuticle (b) epidermis (c) guard cells d) palisade mesophyll

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