Leaf Structure

2.1

Structure of A Leaf

Introduction to Leaf

Leaf is the main organ of a plant which carries out photosynthesis.
The structure of a leaf can be divided into two parts, which are:
- The external structure.
- The internal structure.

The External Structure of a Leaf

Lamina

Lamina is the flat, thin, smooth and green part of the leaf.
Lamina is flat-shaped to provide a wide surface in order to expose the cells containing chloroplasts to the maximum amount of sunlight.
Lamina is also thin to allow gases involved in photosynthesis to diffuse efficiently in the leaf.

Petiole

Vascular tissues in vein transport water,mineral salts and photosynthesis products continuously and effectively.
The network of vein combines to form a main vein and connects to vascular tissues of stem through petiole.
Petiole is the leaf stalk that connects the lamina to the stem of the plant.
The petiole stretches out into the lamina producing a network of middle veins to support the lamina.

The Internal Structure of a Leaf Lamina

In most plants, the leaves grow without overlapping to enable them to receive optimum light to carry out photosynthesis.
Such arrangement is called leaf mosaic.
The diagram below shows the internal structures of a leaf lamina.

Structure of A Leaf	Function
Epidermis	A transparent layer allows sunlight penetration into leaf. Secretes cuticle to reduce water loss from leaf. Protects leaf tissues from injury and entry of pathogens.
Palisade mesophyll	Cylindrical shaped of cells which contain chloroplasts. Can carry out photosynthesis. Closely arrangement of palisade mesophyll cells to absorb sunlight maximally for photosynthesis.
Spongy mesophyll	Irregular shaped of cells which contain chloroplasts. Can carry out photosynthesis. Loosely arrangement of spongy mesophyll cells to form air spaces for carbon dioxide and water evaporation.
Xylem	Transport water and mineral salts from roots to leaf.
Phloem	Transport organic products from leaves to other parts of plants.
Vascular bundle	Component of vascular tissue in plants consisting both phloem and xylem.
Guard cell	Kidney shaped cells on leaf epidermis. Two guard cells join at both cellll ends to form a stoma. Control opening and closing of stomata for gaseous exchange and transpiration.

2.1

Structure of A Leaf

Introduction to Leaf

Leaf is the main organ of a plant which carries out photosynthesis.
The structure of a leaf can be divided into two parts, which are:
- The external structure.
- The internal structure.

The External Structure of a Leaf

Lamina

Lamina is the flat, thin, smooth and green part of the leaf.
Lamina is flat-shaped to provide a wide surface in order to expose the cells containing chloroplasts to the maximum amount of sunlight.
Lamina is also thin to allow gases involved in photosynthesis to diffuse efficiently in the leaf.

Petiole

Vascular tissues in vein transport water,mineral salts and photosynthesis products continuously and effectively.
The network of vein combines to form a main vein and connects to vascular tissues of stem through petiole.
Petiole is the leaf stalk that connects the lamina to the stem of the plant.
The petiole stretches out into the lamina producing a network of middle veins to support the lamina.

The Internal Structure of a Leaf Lamina

In most plants, the leaves grow without overlapping to enable them to receive optimum light to carry out photosynthesis.
Such arrangement is called leaf mosaic.
The diagram below shows the internal structures of a leaf lamina.

Structure of A Leaf	Function
Epidermis	A transparent layer allows sunlight penetration into leaf. Secretes cuticle to reduce water loss from leaf. Protects leaf tissues from injury and entry of pathogens.
Palisade mesophyll	Cylindrical shaped of cells which contain chloroplasts. Can carry out photosynthesis. Closely arrangement of palisade mesophyll cells to absorb sunlight maximally for photosynthesis.
Spongy mesophyll	Irregular shaped of cells which contain chloroplasts. Can carry out photosynthesis. Loosely arrangement of spongy mesophyll cells to form air spaces for carbon dioxide and water evaporation.
Xylem	Transport water and mineral salts from roots to leaf.
Phloem	Transport organic products from leaves to other parts of plants.
Vascular bundle	Component of vascular tissue in plants consisting both phloem and xylem.
Guard cell	Kidney shaped cells on leaf epidermis. Two guard cells join at both cellll ends to form a stoma. Control opening and closing of stomata for gaseous exchange and transpiration.