Chapter: The Fundamental Unit of Life - The Leaf.
The leaf is one of the most important parts of a plant. It is often called the "Kitchen of the Plant" because it prepares food. In this chapter, we will study the structure, types, and functions of leaves in detail.
1. Structure and Parts of a Leaf.
A typical leaf consists of three main parts: the leaf base, the petiole, and the lamina.
[attachment_0](attachment)- Lamina or Leaf Blade: This is the broad, green, and flat part of the leaf. It is the main surface for sunlight absorption.
- Petiole: The stalk that connects the leaf blade to the stem is called the petiole. It holds the leaf towards the light.
- Midrib: The thick vein running through the center of the leaf is called the midrib.
- Veins: Small lines branching out from the midrib are called veins. They transport water and provide support to the leaf.
2. Types of Leaf Venation.
The arrangement of veins on the leaf blade is called venation. There are two main types.
- Reticulate Venation: In this type, the veins form a net-like design on both sides of the midrib. This is commonly found in dicot plants like Rose, Mango, and Hibiscus.
- Parallel Venation: In this type, the veins run parallel to each other. This is commonly found in monocot plants like Grass, Banana, and Wheat.
3. Major Functions of the Leaf.
Leaves perform three vital functions for the survival of the plant.
A. Photosynthesis.
Leaves absorb sunlight and use carbon dioxide from the air and water from the soil to prepare food. This process is essential because it produces glucose and oxygen.
B. Transpiration.
Plants release excess water into the air through tiny pores called stomata. This process helps in cooling the plant and pulling water up from the roots.
C. Gas Exchange.
Leaves act as the lungs of the plant. They take in carbon dioxide and release oxygen during the day.
4. Modifications of Leaves.
Sometimes, leaves change their shape to perform special functions.
- Leaf Spines: In cactus plants, leaves are reduced to spines to reduce water loss.
- Leaf Tendrils: In plants like peas, leaves form coiled structures called tendrils to help the plant climb.
Summary of the Chapter.
The leaf is a vital organ for photosynthesis and transpiration. Understanding the types of venation helps us identify if a plant is a monocot or a dicot.