Notes Chapter 10 Class 7 Science Curiosity NCERT

Life Processes in Plants

1. Plant Growth

• Plants grow by developing new leaves, branches, increasing height, and thickening stems.

Essential Factors:

• Water: Absorbed by roots from soil, keeps plants hydrated.
• Sunlight: Provides energy for growth.
• Nutrients: Minerals from soil support growth.

2. Photosynthesis

• Definition: The process by which plants produce food (glucose) using sunlight.

Requirements:

• Sunlight: Provides energy to drive the process.
• Chlorophyll: Green pigment in leaves that captures sunlight.
• Carbon dioxide (CO₂): Taken from the air through stomata.
• Water: Absorbed by roots from soil.

Products:

• Glucose: Used for energy or stored as starch.
• Oxygen: Released into the air as a byproduct.

Word Equation:

Carbon dioxide + Water → (Sunlight + Chlorophyll) → Glucose + Oxygen

• Main Site: Leaves, known as “food factories,” but other green parts with chlorophyll (e.g., stems) can also perform photosynthesis.
• Importance: Produces food for plants and oxygen for the environment.

3. Role of Leaves in Food Production

• Leaves: Broad, flat structures designed to capture sunlight efficiently.
• Chlorophyll: Green pigment in leaves essential for photosynthesis.
• Starch Storage: Leaves store glucose as starch.

4. Gas Exchange

• Stomata: Tiny pores on the surface of leaves (mostly lower surface).

Function:

• Allow carbon dioxide to enter for photosynthesis.
• Release oxygen produced during photosynthesis.
• Also involved in respiration (exchange of CO₂ and O₂).

5. Transport in Plants

Xylem:

• Tube-like structures in stems, branches, and leaves.
• Transports water and minerals from roots to other parts.

Phloem:

• Tube-like structures that transport food (glucose/starch) from leaves to other parts (e.g., roots, seeds, fruits).
• Food can be stored in roots, seeds, or other parts.

Importance: Ensures all plant parts receive water, minerals, and food for growth and survival.

6. Respiration

• Definition: Process where plants break down glucose to release energy for growth and other functions.

Requirements:

• Glucose: Produced during photosynthesis.
• Oxygen: Taken from the air.

Products:

• Carbon dioxide: Released as a byproduct.
• Water: Released in small amounts.
• Energy: Used for plant growth and activities.

Word Equation:

Glucose + Oxygen → Carbon dioxide + Water + Energy

• Occurrence: Happens in all plant parts (green and non-green), day and night.

7. Importance of Plant Processes

• Photosynthesis: Produces food for plants and oxygen for all living beings, maintaining environmental balance.
• Respiration: Provides energy for plant growth and survival.
• Transport: Ensures water, minerals, and food reach all plant parts.
• Gas Exchange: Supports photosynthesis and respiration through stomata.
• Balance in Nature: Photosynthesis and respiration maintain CO₂ and O₂ levels in the atmosphere.