Quick Introduction

Plants are living organisms that carry out life processes to survive, grow and reproduce. Chapter 10 of Class 7 NCERT — Life Processes in Plants — explains how plants obtain food, breathe, transport materials, and get rid of wastes. This revision module summarises the important concepts in a concise, exam-oriented manner so you can revise effectively before tests and board-level assessments.

1. Nutrition in Plants (Autotrophic & Heterotrophic)

Most plants are autotrophs — they prepare their own food using carbon dioxide, water and sunlight in a process called photosynthesis. Chlorophyll, present in chloroplasts, captures sunlight. The overall simplified equation is:

6CO₂ + 6H₂O + light energy —> C₆H₁₂O₆ + 6O₂

Key points to remember: photosynthesis occurs mainly in leaves, especially the green parts; stomata help in gas exchange; not all plants are fully autotrophic — some are parasitic (e.g., Cuscuta), while others are saprophytic and obtain nutrients from dead organic matter.

2. Structure of a Leaf — Adaptations for Photosynthesis

A typical leaf is designed for efficient photosynthesis. Important structures include:

• Cuticle — waxy layer that reduces water loss.
• Upper epidermis — transparent layer allowing light in.
• Palisade mesophyll — tightly packed cells rich in chloroplasts; main site of photosynthesis.
• Spongy mesophyll — loosely packed cells for gas circulation.
• Veins (xylem and phloem) — transport water, minerals and food.
• Stomata — pores on leaf surface for gas exchange and transpiration; guarded by guard cells.

3. Photosynthesis — Detailed Notes

Photosynthesis requires three essentials: light, carbon dioxide and water. Chlorophyll captures light energy and converts it into chemical energy. Oxygen released during the process is a byproduct and is vital for life on Earth. Factors affecting photosynthesis include light intensity, carbon dioxide concentration, temperature, and amount of chlorophyll. In exam answers, state the raw materials explicitly and mention that glucose produced may be stored as starch — many questions ask for the test for starch (iodine test).

4. Respiration in Plants

Respiration is the process of releasing energy from food (glucose). Plants respire all the time — day and night — because energy is needed for growth and maintenance. Most plant respiration is aerobic (uses oxygen); anaerobic respiration happens when oxygen is scarce (e.g., waterlogged conditions) and leads to formation of ethanol and carbon dioxide. Don’t confuse respiration with photosynthesis: photosynthesis stores energy, respiration releases energy.

5. Transport of Water and Minerals — Xylem & Transpiration

Water absorption and transport is essential. Roots absorb water and minerals from soil via root hairs. Xylem vessels transport water and dissolved minerals upward from roots to leaves. Transpiration — loss of water vapour from plant surfaces (mostly leaves) — creates a transpiration pull that helps in upward movement of water. Factors affecting transpiration include temperature, humidity, wind, and light. Plants adapted to dry conditions (xerophytes) have features like thick cuticle, reduced leaves, and sunken stomata to reduce water loss.

6. Transport of Food — Phloem & Translocation

Food produced in the leaves (mainly as sugars) is transported to other parts of the plant (growing regions, storage organs) via the phloem. This movement is called translocation and is bidirectional — from source (leaf) to sink (root, fruit, growing tissues). Explain that unlike xylem which mainly moves water upward, phloem moves organic nutrients in any direction depending on plant needs.

7. Excretion & Waste Removal in Plants

Plants do not have specialised excretory organs like animals. They remove wastes in several ways: some waste products accumulate in leaves, bark or latex and get shed; some are stored in vacuoles or in non-living parts; gases like oxygen are released through stomata; extra water is lost by transpiration. Also mention plant exudates — resins and gums — as examples of substances that are removed from plants.

8. Practicals and Diagrams Often Asked in Exams

Important experiments and observations to master:

• Testing leaves for starch (demonstrates photosynthesis) — de-starch, place in sunlight, iodine test.
• Observation of stomata under microscope — leaf peel or temporary mount.
• Transpiration demonstration — with a potometer or by covering a leafy shoot and looking for condensation.
• Simple root and stem transverse sections and identifying xylem and phloem in diagrams.

9. Important Definitions & Key Terms

10. Quick Revision Checklist (Write these down!)

1. Be able to write the photosynthesis equation and name raw materials and products.
2. Know the structure of a typical leaf and function of each part (cuticle, epidermis, mesophyll, veins, stomata).
3. Explain how water moves from root to leaf and how transpiration helps.
4. Distinguish between xylem and phloem (structure and function).
5. Describe simple tests: starch test, stomatal observation, transpiration setup.

11. Common Short Answer & Long Answer Questions (Exam-oriented)

Short answer style prompts:

• Define photosynthesis and give its importance.
• Describe two adaptations of leaves in xerophytes to reduce water loss.
• What is translocation? How is it different from transpiration?

Long answer style prompts:

• Describe the structure of a leaf and explain how it is adapted for photosynthesis with labelled diagram (6–8 marks).
• Explain the process of transpiration and describe an experiment to show transpiration in plants (5–6 marks).

12. Exam Tips & Time-saving Strategies

13. Sample 5-Minute Answer Plan (For 8-mark question)

1. Begin with a one-line definition and importance (1 mark).
2. Give a neat labelled diagram (2 marks).
3. Explain major parts and their roles in 3–4 short points (3 marks).
4. Finish with a concluding sentence that links structure to function (1 mark).

Conclusion — Takeaway Points

Chapter 10 connects how plants make food (photosynthesis), move substances (xylem and phloem), breathe (respiration), and keep their internal environment stable (transpiration and waste removal). Focus on understanding the process and practising a few standard diagrams and experiments — this will ensure strong performance in CBSE Class 7 assessments.