Class 7 Science Nutrition in Plants Notes

Introduction:
The chapter “Nutrition in Plants” explores how plants prepare their own food through the process of photosynthesis. Just like humans and animals need food for energy and growth, plants also need food, but they make it themselves using sunlight, water, and carbon dioxide. This chapter helps students understand the importance of sunlight, chlorophyll, and various nutrients for plant growth and health.

Key Concepts Covered:

1. What is Nutrition?
   • Nutrition is the process of obtaining and using food to obtain energy and build body structures.
   • Plants, unlike animals, make their own food through a process called photosynthesis.
2. Modes of Nutrition in Plants:
   • Autotrophic Nutrition: Plants make their own food. They use sunlight, water, and carbon dioxide to produce glucose (a type of sugar) and oxygen.
   • Heterotrophic Nutrition: Some plants, like carnivorous plants (e.g., Venus flytrap), depend on other organisms for food. They are not capable of photosynthesis.
3. Photosynthesis – The Process of Making Food:
   • The process of photosynthesis occurs in the leaves of the plant, specifically in the chloroplasts (which contain chlorophyll).
   • Photosynthesis Formula:
     $6CO_2 + 6H_2O + \text{light energy} \rightarrow C_6H_{12}O_6 + 6O_2$6CO2​+6H2​O+light energy→C6​H12​O6​+6O2​
     This means:
     • Carbon dioxide from the air,
     • Water absorbed by roots,
     • In the presence of light and chlorophyll,
     • Produces glucose (food) and oxygen.
4. Chlorophyll – The Green Pigment:
   • Chlorophyll is a green pigment present in plant cells that helps in trapping sunlight.
   • Without chlorophyll, plants would not be able to absorb light energy and carry out photosynthesis.
5. The Importance of Sunlight:
   • Sunlight is the primary source of energy for photosynthesis. The chlorophyll in the leaves absorbs sunlight and uses it to convert carbon dioxide and water into food.
6. Factors Affecting Photosynthesis:
   • The rate of photosynthesis can be affected by several factors, including:
     • Light intensity: More light results in a higher rate of photosynthesis.
     • Concentration of carbon dioxide: A higher concentration of CO2 increases the rate of photosynthesis.
     • Temperature: If the temperature is too high or low, photosynthesis slows down.
7. Mineral Nutrition in Plants:
   • Plants require minerals for proper growth. These minerals include nitrogen, phosphorus, potassium, magnesium, etc.
   • These minerals are absorbed by the roots from the soil.
8. Absorption of Water by Roots:
   • Roots absorb water from the soil through osmosis and transport it to the leaves for photosynthesis.
   • The xylem vessels are responsible for transporting water and nutrients from the roots to the rest of the plant.

Important Questions with Answers:

1. What is photosynthesis?
   • Answer: Photosynthesis is the process by which plants make their own food using sunlight, water, and carbon dioxide, producing glucose and oxygen.
2. What is the role of chlorophyll in photosynthesis?
   • Answer: Chlorophyll absorbs sunlight, which helps the plant convert carbon dioxide and water into glucose and oxygen during photosynthesis.
3. What are the raw materials required for photosynthesis?
   • Answer: The raw materials required for photosynthesis are carbon dioxide, water, and sunlight.
4. Explain the importance of sunlight in the process of photosynthesis.
   • Answer: Sunlight provides the energy needed for photosynthesis to occur. Without sunlight, plants cannot produce food.
5. Why do plants need minerals?
   • Answer: Plants need minerals like nitrogen, phosphorus, and potassium for proper growth, development, and the formation of flowers, fruits, and seeds.
6. What is the process of water absorption in plants?
   • Answer: Water is absorbed by the roots from the soil through osmosis and transported to the leaves by the xylem vessels.