Science · Class 7 · Chapter 10
Life Processes in Plants
Aim: Build a clear, working understanding of this chapter's key ideas, connected to real NCERT examples, worked problems, and everyday situations.
- Chlorophyll — The green pigment that captures sunlight.
- Starch — The stored form of a plant's food.
- Photosynthesis — Making food using sunlight, CO2, and water.
- Stomata — Tiny pores for gas exchange on a leaf.
- Xylem — Carries water and minerals upward.
- Phloem — Carries food to the rest of the plant.
- Respiration — Releasing energy from glucose using oxygen.
- Glucose — The simple sugar made by photosynthesis.
Chapter 10 · Concept 1 of 10
How Do Plants Grow?
- Three potted plants tested different conditions.
- Sunlight + water — Grew best of all three.
- Sunlight, no water — The plant likely died.
- Dark + water — Grew poorly despite water.
Chapter 10 · Concept 2 of 10
Leaves: The Food Factories
- Chlorophyll — The green pigment in leaves that captures sunlight efficiently — it's why most leaves are green.
- Starch — The carbohydrate form in which plants store their food.
Chapter 10 · Concept 3 of 10
The Iodine Test
- A decolourised leaf treated with iodine turns blue-black if starch is present.
- Only where there's chlorophyll and sunlight — Only the green, sunlit parts of a leaf test positive for starch — parts kept in the dark, or non-green patches, do not.
Chapter 10 · Concept 4 of 10
Carbon Dioxide Is Essential Too
- Proven by denying it — A leaf part sealed away from carbon dioxide (using a CO2-absorbing chemical) does not form starch, while the exposed part does.
Chapter 10 · Concept 5 of 10
Photosynthesis
- Plants use sunlight and chlorophyll to convert carbon dioxide and water into food, releasing oxygen.
- Carbon dioxide + Water →(Sunlight, Chlorophyll)→ Glucose + Oxygen — Glucose is used instantly for energy, or converted to starch for storage.
Chapter 10 · Concept 6 of 10
Photosynthesis Releases Oxygen
- The glowing matchstick test — A water plant kept in sunlight releases a gas that relights a glowing matchstick — proof that the gas is oxygen.
Chapter 10 · Concept 7 of 10
Gas Exchange: Stomata
- Stomata — Tiny pores, usually on a leaf's lower surface, that let carbon dioxide and oxygen move in and out during photosynthesis and respiration.
Chapter 10 · Concept 8 of 10
Transport in Plants
- Leaves (food made here)
- Roots (water absorbed here)
Chapter 10 · Concept 9 of 10
Respiration in Plants
- Germinating seeds turn lime water milky — even in the dark — showing they respire.
- Glucose + Oxygen → Carbon dioxide + Water + Energy — Every part of a plant, green or not, respires — the energy released supports growth and development.
Chapter 10 · Concept 10 of 10
Photosynthesis vs Respiration
- | Photosynthesis | Respiration
- Raw materials — Carbon dioxide + water (+ sunlight, chlorophyll) — Glucose + oxygen
- Products — Glucose + oxygen — Carbon dioxide + water + energy
- Importance — Makes food and releases oxygen — Releases energy for growth
Quick Recap
Check Your Understanding
- 1Complete the table comparing photosynthesis and respiration: raw materials, products, word equation, and importance of each.
- 2Imagine every photosynthesising organism on Earth disappeared. What impact would this have on living things?
- 3A potato slice tests positive for starch with iodine. Where does this starch come from, and how does it reach the potato?