Plant Life and Its Structure

1. Introduction

Plants are living organisms that can make their own food. They are essential for life on Earth as they produce oxygen and form the base of most food chains.

A plant has four main parts: root, stem, leaf, and flower.

2. The Root System

Roots grow underground and anchor the plant in the soil.

Types of Roots

Functions of Roots

1. Anchoring: Fixes the plant firmly in the soil.
2. Absorption: Absorbs water and minerals from the soil.
3. Storage: Some roots store food (carrot, radish, sweet potato, beetroot).
4. Support: Prop roots in banyan provide additional support.

Worked Example: Classify as tap root or fibrous root: (a) Mango (b) Grass (c) Carrot (d) Wheat.

(a) Mango: Tap root. (b) Grass: Fibrous root. (c) Carrot: Tap root (modified for storage). (d) Wheat: Fibrous root.

3. Venation

The arrangement of veins on a leaf is called venation.

Relationship between root type and venation:

• Plants with tap roots usually have reticulate venation.
• Plants with fibrous roots usually have parallel venation.

Exam Focus (2 marks): 'If a plant has fibrous roots, what type of venation would its leaves likely show?'

Fibrous roots usually have leaves with parallel venation (e.g., grass, wheat).

4. The Stem

The stem is the part of the plant that grows above the ground.

Functions of the Stem

1. Support: Holds the leaves, flowers, and fruits.
2. Transport: Carries water and minerals from roots to leaves (xylem) and food from leaves to other parts (phloem).
3. Storage: Some stems store food (potato, ginger, onion).
4. New growth: Bears buds that grow into branches, leaves, and flowers.

Types of Stems

Common Mistake: Calling a potato a root. Potato is a modified stem (tuber) that grows underground and stores food. It has buds ('eyes') that can grow into new plants.

5. The Leaf

Leaves are the food-making factories of the plant.

Parts of a Leaf

1. Leaf blade (lamina): The flat, green part.
2. Petiole: The stalk attaching the leaf to the stem.
3. Veins: Transport water and food; provide support.
4. Midrib: The central vein.

Photosynthesis — A Brief Introduction

Photosynthesis is the process by which green plants make their own food using sunlight, carbon dioxide, and water.

Equation: Carbon dioxide + Water -> (Sunlight, Chlorophyll) -> Glucose + Oxygen

Requirements:

• Sunlight (energy source).
• Chlorophyll (green pigment in leaves).
• Carbon dioxide (from air).
• Water (from soil).

Products: Glucose (food for the plant), Oxygen (released into the air).

Exam Focus (3 marks): 'What is photosynthesis? Write the word equation.'

Photosynthesis is the process by which green plants make food using sunlight, water, and carbon dioxide in the presence of chlorophyll. Carbon dioxide + Water -> Glucose + Oxygen.

6. The Flower

The flower is the reproductive part of the plant.

Parts of a Flower

Common Mistake: Thinking all flowers are colourful. Some flowers are small and dull (grass flowers, wheat flowers) because they are pollinated by wind, not insects.

7. Self-Test

1. Differentiate between tap root and fibrous root with examples.
2. Name the type of venation found in: (a) Mango leaf (b) Grass leaf.
3. List three functions of the stem.
4. Label the parts of a leaf.
5. What is photosynthesis? Name its requirements.
6. Name the male and female parts of a flower.
7. Why is a potato considered a stem and not a root?

8. Answers to Self-Test

1. Tap root: one main root (mango). Fibrous root: many thin roots (grass).
2. (a) Reticulate venation (b) Parallel venation.
3. Supports leaves and flowers, transports water and food, stores food (potato).
4. Leaf blade (lamina), petiole, veins, midrib.
5. The process by which green plants make their own food using sunlight, CO2, and water. Requirements: sunlight, chlorophyll, CO2, water.
6. Male: stamen (anther + filament). Female: pistil (stigma + style + ovary).
7. Potato has buds ('eyes') that can grow into new plants, which is a characteristic of stems. It also stores food like a modified stem.