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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.

This image is a detailed diagram of a leaf's internal structure. It shows various layers and components, including: - **Cuticle**: A waxy, protective layer on the surface. - **Upper epidermis**: The outermost layer of cells on the upper side. - **Palisade mesophyll**: A layer of elongated cells rich in chloroplasts, located below the upper epidermis. - **Spongy mesophyll**: Loosely packed cells with air spaces, found beneath the palisade mesophyll. - **Air space**: Gaps between spongy mesophyll cells that allow gas exchange. - **Lower epidermis**: The outermost layer of cells on the lower side. - **
 
This image is a diagram titled ‘Structure of A Leaf.’ It features a central blue circle with the title, surrounded by six orange and yellow pentagons. Each pentagon is labeled with a different part of the leaf structure: 1. Epidermis 2. Palisade mesophyll 3. Spongy mesophyll 4. Xylem 5. Phloem 6. Vascular bundle 7. Guard cell The diagram is designed to visually represent the different components of a leaf's structure.
 
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.
 

 

 

 

 

 

 

The views expressed in the notes here are those of the contributor and don’t necessarily represent the views of Pandai.
Chapter : Structure and Leaf Function
Topic : Leaf Structure
Form 5 Biology
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