Life Processes in Plants – Class 7 Science Chapter 10 Notes & NCERT PDF

Class 7ScienceChapter 10NCERT book: Curiosity - Science Class 7

Notes and a simple summary of Chapter 10 of the NCERT Class 7 Science book, with the official chapter PDF, flashcards, an MCQ quiz and an AI tutor for your doubts.

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Chapter 10: Life Processes in Plants

Introduction

Animals eat food to grow — but have you ever seen a plant eat? As plants grow, new leaves and branches appear, height increases and the stem thickens. Students in the chapter suggest ideas: water helps, sunlight helps, maybe plants take food from the soil. This chapter tests such ideas with experiments and explains how plants make, move and use their food.

"Trees do not produce fruits and flowers merely because they are planted." — Vrikshayurveda, an ancient Indian text on plant growth, soil and farming (it even describes organic manure made from water, barley and seeds like green, black and horse gram).

Key Concepts

10.1 How do plants grow?

Activity 10.1 grows chilli/tomato saplings in three pots: A (sunlight + water), B (sunlight, no water), C (dark + water). Pot A grows best, C grows poorly, and B may die. Plants need both sunlight and water to grow.

10.2 How do plants get food?

Leaves are the 'food factories' of plants. Plants store food as starch, made in leaves, which are generally broad and flat and green due to chlorophyll, a pigment that captures sunlight efficiently.

  • Starch test (Activity 10.2): Boil the leaf to soften it, decolourise it in alcohol (in a test tube placed in a hot-water bath — never directly near flame), then add dilute iodine. Blue-black = starch present. Decolourising makes the colour change easy to see.
  • Role of sunlight and chlorophyll (Activity 10.3, Bhaskar): Variegated leaves (green and non-green patches) from a plant in sunlight and one kept 36 hours in the dark. Only the green patches of the sunlit leaf turned blue-black; the dark-kept leaf showed no starch anywhere. Chlorophyll and sunlight are essential for making starch.
  • Role of air (Activity 10.4): A destarched plant (kept 2–3 days in the dark) has half a leaf inside a bottle with caustic soda, which absorbs carbon dioxide. After sunlight, only the outside half shows starch. Carbon dioxide is essential.
  • Oxygen is released (Activity 10.5, Barkha didi): A water plant under a funnel and inverted test tube gives bubbles in sunlight but not in the dark. The collected gas makes a lit matchstick burn with an intense flame — it is rich in oxygen.
    • Photosynthesis is the process by which plants prepare food in the presence of sunlight and chlorophyll.
    Carbon dioxide + Water —(sunlight, chlorophyll)→ Glucose + Oxygen

    Food is first made as glucose (a simple carbohydrate), used for instant energy and later converted to starch for storage. The leaf is the main site, but other green parts with chlorophyll also photosynthesise. Leaves that look red, violet or brown have other pigments hiding the green; they still photosynthesise.

    Gas exchange — stomata

    In Activity 10.6, a thin peel from the lower surface of a leaf (rhoeo, money plant, onion, hibiscus, coleus, grass) is stained with ink and seen under a microscope. Tiny pores called stomata are visible. Stomata help in the exchange of gases (carbon dioxide and oxygen).

    10.3 Transport in plants

  • Water and minerals: Roots absorb water with minerals from soil. In Activity 10.7, a white-flowered twig (sadabahar, balsam) in red-ink water shows red in stem, leaves and flowers the next day. Water rises through thin tube-like xylem.
  • Food: Food made in leaves travels to all parts through another set of tubes — phloem — and may be stored in seeds and roots (and tubers like potato).

    • 10.4 Do plants respire?

    Activity 10.8: soaked moong seeds on wet cotton in a closed flask for 24 hours in the dark; air from the flask turns lime water milky — the germinating seeds released carbon dioxide by respiration.

    Glucose + Oxygen → Carbon dioxide + Water + Energy

    All parts of a plant, green or non-green, respire, and the energy is used for growth and development. Stomata help in gas exchange for both photosynthesis and respiration.

    Key Scientists

  • Rustom Hormusji Dastur (1896–1961), head of Botany at the Royal Institute of Science, Bombay (1921–1935), studied how water, temperature and the colour of light affect photosynthesis.
  • Kamala Sohonie (1911–1998) earned a PhD from Cambridge for work on respiration in plants, later became Director at the Royal Institute of Science, Bombay, and worked on Neera, a nutritious drink from coconut palm sap.

    • Key Terms

  • Photosynthesis (प्रकाश-संश्लेषण) — making food using sunlight and chlorophyll
  • Chlorophyll (पर्णहरित) — green pigment that captures sunlight
  • Starch (मंड / स्टार्च) — stored food of plants
  • Glucose (ग्लूकोज़) — simple sugar made first in photosynthesis
  • Stomata (रंध्र) — tiny pores for gas exchange
  • Xylem (जाइलम / दारु) — carries water and minerals upward
  • Phloem (फ्लोएम / पोषवाह) — carries food to all parts
  • Destarching (मंड-रहित करना) — removing stored starch by keeping a plant in the dark
  • Decolourise (रंगहीन करना) — remove the green colour of a leaf using alcohol
  • Minerals (खनिज) — nutrients from soil
  • Respiration (श्वसन) — breaking glucose with oxygen to release energy
  • Caustic soda (कास्टिक सोडा / सोडियम हाइड्रॉक्साइड) — absorbs carbon dioxide

    • Real-life Connections

  • Greenhouses control light, water and carbon dioxide to grow better crops.
  • A sealed bottle garden keeps growing because CO₂ from respiration is used in photosynthesis and O₂ from photosynthesis is used in respiration.
  • Potatoes are full of starch made in the leaves and carried down through phloem.
  • Safety: alcohol is flammable (keep it away from direct heat); caustic soda can burn skin (only teachers should handle it).

    • Common Misconceptions

  • "Plants take food from the soil." — Soil gives water and minerals; plants make food in leaves.
  • "Plants respire only at night" or "Only animals respire." — All plant parts respire all the time; photosynthesis needs sunlight.
  • "Non-green patches have no chlorophyll at all." — They may just not have enough chlorophyll to make detectable starch.
  • "Xylem carries food." — Xylem carries water and minerals; phloem carries food.
  • "Red leaves cannot photosynthesise." — Other pigments hide chlorophyll; an iodine test can still show starch.

    • Keep the Curiosity Alive (exercise hints)

  • Photosynthesis: raw materials CO₂ + water (with sunlight, chlorophyll); products glucose + oxygen. Respiration: glucose + oxygen → CO₂ + water + energy.
  • X + Y → carbon dioxide + Z + energy: X = glucose, Y = oxygen, Z = water.
  • Broad, flat leaves catch more sunlight — more efficient photosynthesis.
  • Vani's set-ups: starch and oxygen only in (a) sunlight with CO₂.
  • If all photosynthesising organisms disappeared, food and oxygen for living beings would run out.

    • 💡 Key Learning Points

    • ✓Plants need sunlight and water to grow, and they make their own food in leaves — the 'food factories'.
    • ✓Photosynthesis needs sunlight, water, carbon dioxide and chlorophyll, and produces glucose (stored as starch) and oxygen.
    • ✓The iodine test (blue-black) shows starch; experiments with variegated and destarched leaves prove the roles of chlorophyll, sunlight and carbon dioxide.
    • ✓Stomata on leaves exchange gases; xylem carries water and minerals up, phloem carries food to all parts.
    • ✓All parts of a plant respire: glucose + oxygen → carbon dioxide + water + energy.

    👨‍🏫 Teaching Tips

    • →Set up Activity 10.1 (three pots) two weeks in advance so students can measure height and count leaves on Day 1 and after 2 weeks.
    • →Demonstrate the leaf starch test carefully using a water bath for the alcohol; stress the flammability caution.
    • →Use a variegated leaf (croton/coleus) and ask students to predict where blue-black will appear before testing.
    • →Show the red-ink twig activity overnight and let students cut the stem to see coloured xylem with a magnifying glass.
    • →Prepare a leaf peel with ink to show stomata under a microscope, or project a microscope image.
    • →Make a class chart comparing photosynthesis and respiration (raw materials, products, word equation, importance).
    • →Discuss the bottle garden to connect photosynthesis and respiration as a balance in nature.

    📋 Assessment Questions

    1. Can the student state what each pot in Activity 10.1 shows about sunlight and water?
    2. Can the student explain the steps and purpose of the leaf starch test?
    3. Can the student interpret the variegated leaf and caustic soda experiments?
    4. Can the student write the word equations of photosynthesis and respiration and name their raw materials and products?
    5. Can the student describe the roles of stomata, xylem and phloem?

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    All chapters in Curiosity - Science Class 7

    1. 1. The Ever-Evolving World of Science
    2. 2. Exploring Substances: Acidic, Basic, and Neutral
    3. 3. Electricity: Circuits and their Components
    4. 4. The World of Metals and Non-metals
    5. 5. Changes Around Us: Physical and Chemical
    6. 6. Adolescence: A Stage of Growth and Change
    7. 7. Heat Transfer in Nature
    8. 8. Measurement of Time and Motion
    9. 9. Life Processes in Animals
    10. 10. Life Processes in Plants
    11. 11. Light: Shadows and Reflections
    12. 12. Earth, Moon, and the Sun