Rapid Revision – Class 7 Science -Chapter 1- Nutrition in Plants – Complete Notes

Revision Notes – Chapter 1- Nutrition in Plants

Nutrition in Plants

1. Nutrition in Plants

  • Definition- The process by which plants obtain and use substances for growth, development, and metabolic activities.
  • Importance- Essential for energy, building materials, and nutrients for photosynthesis, respiration, reproduction, health, and resistance to diseases.

Also Check – Chapter 1- Nutrition in Plants -Class 7 – Detailed Notes

2. Types of Nutrients

  • Macronutrients- Required in large quantities.
    • Carbon (C)- For building organic compounds.
    • Hydrogen (H) and Oxygen (O)- Formation of water and organic compounds.
    • Nitrogen (N)- Synthesis of proteins, enzymes, chlorophyll.
    • Phosphorus (P)- Energy transfer, DNA, RNA, ATP synthesis.
    • Potassium (K)- Osmoregulation, enzyme activation, protein synthesis.
    • Calcium (Ca)- Cell wall formation, membrane stability, enzyme activation.
    • Magnesium (Mg)- Component of chlorophyll, essential in photosynthesis.
  • Micronutrients- Needed in smaller quantities.
    • Iron (Fe), Zinc (Zn), Copper (Cu), Manganese (Mn), Molybdenum (Mo), Boron (B), Chlorine (Cl)- Crucial for enzyme activation, electron transport, and metabolic reactions.

Also Check – Nutrition in Plants – Class 7 Questions with Answers Worksheet

3. Mineral Requirements for Plant Growth

  • Each mineral nutrient serves specific functions.
  • Deficiencies can lead to problems like stunted growth, yellowing of leaves, poor root development, and reduced disease resistance.


4. Photosynthesis

  • Definition- Process where green plants, algae, and some bacteria convert sunlight into chemical energy (glucose).
  • Process- Involves light-dependent reactions and light-independent reactions (Calvin cycle).
  • CO2 and H2O are converted into glucose (C6H12O6) and oxygen (O2).
  • Takes place in chloroplasts of plant cells.

5. Chlorophyll in Photosynthesis

  • Chlorophyll- Green pigment in chloroplasts, captures light energy from the sun.
  • Absorbs light in the blue and red regions and reflects green light.
  • Arranged in photosystems for converting light energy into chemical energy.

6. Sunlight in Photosynthesis

  • Role- Primary energy source for photosynthesis.
  • Absorption- Chlorophyll pigments absorb light, mainly in red and blue wavelengths; green light is mostly reflected.
  • Energy Conversion- Light energy is transformed into chemical energy in the form of ATP and NADPH.
  • Importance- Essential for oxygen production and conversion of light energy to chemical energy stored in glucose.

Also Check – NCERT Solutions for Class 7 Science Chapter 1: Nutrition In Plants

Plant Processes

7. Stomata and Gas Exchange

  • Structure- Tiny openings on plant surfaces, surrounded by guard cells.
  • Function- Control entry of CO2 for photosynthesis and exit of O2 and H2O vapour.
  • Mechanism- Stomata open when guard cells are turgid and close when flaccid.

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8. Transpiration

  • Process- Loss of water vapour through leaves, mainly via stomata.
  • Functions-
    • Cooling the plant through evaporative cooling.
    • Creating a transpiration pull for upward movement of water and minerals.
    • Nutrient transport and maintenance of cell turgidity.
  • Relation to Photosynthesis- Opens stomata for CO2 entry, leading to water loss but necessary for photosynthesis.

9. Absorption of Water and Minerals

  • Roots’ Role- Crucial in absorbing water and minerals from the soil.
  • Root Hairs- Increase surface area for absorption.
  • Water Absorption- Through osmosis, driven by concentration gradients.
  • Mineral Absorption- Via active transport (against concentration gradient) and passive diffusion.
  • Transport- Water and minerals are moved upwards through xylem vessels, aided by transpiration pull.

Photosynthesis Equation

10. Photosynthesis Equation

  • Equation- 6CO2 + 6H2O -> C6H12O6 + 6O2
  • Reactants- Carbon dioxide (CO2) and water (H2O).
  • Products- Glucose (C6H12O6) and oxygen (O2).
  • Process- Uses light energy to convert CO2 and H2O into glucose and oxygen.

11. Components of Photosynthesis

  • Carbon Dioxide (CO2)- Obtained from air through stomata, essential for photosynthesis.
  • Water (H2O)- Absorbed from soil, provides hydrogen for glucose.
  • Glucose (C6H12O6)- Primary product, energy-rich molecule for metabolic processes.
  • Oxygen (O2)- By-product, released into the atmosphere.

Plant Nutrition

12. Synthesis of Nutrients in Plants

  • Proteins- Made from amino acids; crucial for structure, enzyme functions, cell signalling.
  • Fats (Lipids)- Source of energy; involved in membrane formation, energy storage.
  • Vitamins- Facilitate enzyme activity; support growth, development, defence mechanisms.

13. Importance of Nutrients for Plant Growth

  • Proteins- Building blocks of cells; involved in photosynthesis, respiration, DNA replication.
  • Fats (Lipids)- Energy reserve; structural integrity of cell membranes, temperature regulation.
  • Vitamins- Aid in metabolic pathways, stress tolerance, synthesis of hormones.

Other Modes of Nutrition in Plants

14. Heterotrophic Nutrition

  • Definition- Plants obtaining food from external sources, not capable of photosynthesis.
  • Types- Parasitic, insectivorous, and saprotrophic plants.

15. Parasitic Plants

  • Characteristics- Depend on host plants for nutrients; have little or no chlorophyll.
  • Adaptations- Specialised roots or haustoria to penetrate host tissues.
  • Examples- Mistletoe, dodder, Rafflesia.

16. Insectivorous (Carnivorous) Plants

  • Habitat- Grow in nutrient-poor soils.
  • Mechanism- Trap and digest insects for essential nutrients, especially nitrogen.
  • Examples- Venus flytrap, pitcher plants, sundews.

17. Saprotrophic Nutrition

  • Definition- Decomposing dead organic matter for nutrition.
  • Role in Ecosystem- Recycle nutrients, enrich soil.
  • Examples- Fungi (mushrooms, molds), certain bacteria.

18. Symbiotic Relationships in Nutrition

  • Symbionts- Organisms that form beneficial relationships with plants.
  • Nutrient Exchange- Provide nutrients like nitrogen, phosphorus to host plants.
  • Examples- Nitrogen-fixing bacteria, mycorrhizal fungi.

19. Lichens-

  • Composition- Symbiotic association between a fungus and an alga or cyanobacterium.
  • Role- Contribute to soil formation and nutrient cycling in harsh environments.

Transport of Food in Plants

20. Transport of Food in Plants

  • Vascular Tissues- Xylem and Phloem.
  • Xylem- Transports water and minerals from roots; made of tracheary elements.
  • Phloem- Transports food, mainly sugars, from leaves; consists of sieve elements and companion cells.

Translocation in Plants

21. Translocation in Plants

  • Process- Movement of food substances, primarily sugars, through the phloem.
  • Sources and Sinks- From sources (leaves) to sinks (growing roots, fruits, storage tissues).
  • Mechanism- Pressure flow mechanism; sugars transported into sieve tubes create a pressure gradient.
  • Importance- Distributes food for growth, respiration, storage; ensures even nutrient supply.

Nutrient Replenishment in Plants

22. Nutrient Absorption and Replenishment

  • Absorption- Plants absorb minerals and nutrients from the soil through roots.
  • Soil Depletion- Continuous nutrient uptake decreases soil nutrient availability.
  • Fertilisers and Manures- Replenish soil nutrients, ensuring healthy plant growth.

23. Nitrogen Deficiency and Rhizobium Bacteria

  • Nitrogen Demand- High in crop plants; leads to soil nitrogen deficiency.
  • Nitrogen Fixation- Rhizobium bacteria convert atmospheric nitrogen into soluble form.
  • Symbiotic Relationship- Rhizobium and leguminous plants (e.g., gram, peas, beans).
  • Farmer’s Advantage- Reduces need for nitrogenous fertilisers; sustainable nitrogen source.

24. Importance of Leguminous Plants

  • Role in Agriculture- Acquire nitrogen from the atmosphere, enrich soil nutrients.
  • Dietary Significance- Source of legumes (dals), vital in human nutrition.

Quick Review Tips

  • Focus on the functions of macronutrients and micronutrients.
  • Understand the basic steps of photosynthesis and the role of chlorophyll.
  • Remember the effects of nutrient deficiencies on plant health.
  • Understand the roles of sunlight, stomata, and transpiration in photosynthesis.
  • Familiarise with the process and importance of water and mineral absorption through roots.
  • Highlight the connection between these processes and their overall impact on plant health and growth.
  • Focus on the key elements of the photosynthesis equation.
  • Understand the roles of CO2, H2O, glucose, and O2 in photosynthesis.
  • Remember the types of nutrients synthesised by plants and their significance for growth and development.
  • Understand different heterotrophic nutrition modes in plants and their specific adaptations.
  • Familiarise with the role of symbiotic relationships in plant nutrition.
  • Remember the functions of xylem and phloem in the transport of nutrients within plants.
  • Focus on understanding the translocation process and its significance in plant growth.
  • Remember the role of fertilisers and manures in nutrient replenishment.
  • Recognize the importance of Rhizobium bacteria and leguminous plants in natural nitrogen fixation.

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