Willer Academy

Nation Builders Through Education | Founded by Er. Rahul Kumar Dubey Sir

Chapter 1: Nutrition in Plants

Subject: Science (Physics, Chemistry, Biology)

Class: 7

Series: Base Builder for Moderate to Hard

Learning Objectives

By the end of this chapter, you, the future scientist and nation-builder, will be able to:

1. Define nutrition and identify the different modes of nutrition in plants.
2. Explain the process of photosynthesis in detail, including the chemical equation.
3. Conduct experiments to prove that sunlight and chlorophyll are necessary for photosynthesis.
4. Understand other modes of nutrition like parasitic and symbiotic relationships.
5. Solve numerical problems based on the efficiency of photosynthesis and growth.
6. Apply this knowledge to real-world agricultural and environmental situations.

1.1 Introduction: Why do we eat? Why do Plants need Food?

Just like you need a nutritious lunchbox to study, play, and grow, plants also need food. This food gives them energy to perform their life activities. The process of taking in food and its utilization by the body is called Nutrition.

Quick Check

What did you have for breakfast? That's your nutrition! Now, think about a giant Banyan tree in our schoolyard. It doesn't eat chips or oranges. So, how does it get its nutrition? Let's find out!

1.2 Modes of Nutrition

Plants have two primary ways of getting their food:

1. Autotrophic Nutrition (Auto = self, Trophos = nourishment)

• Plants are called autotrophs because they make their own food.
• They use simple inorganic substances like carbon dioxide and water to prepare complex organic food (like glucose).

2. Heterotrophic Nutrition (Heteros = other)

• Some plants cannot make their own food. They depend on other plants or organisms. These are called heterotrophs.
• Examples: Parasites like Cuscuta (Amarbel), insectivorous plants like the Venus flytrap.

Task 1

Look around your home or school garden. Can you spot any yellow, thread-like plant growing on a hedge? That might be Cuscuta, a parasite! Draw a quick sketch of it in your notebook.

1.3 The Magic Kitchen: Photosynthesis

This is the process by which green plants make their own food using sunlight. It's the most important chemical reaction on Earth! Without it, there would be no life.

The word Photosynthesis can be broken down as:

• Photo = Light
• Synthesis = To build (Building up using light)

Raw Materials Required:

1. Carbon Dioxide (CO₂): Enters the leaves from the air through tiny pores called stomata.
2. Water (H₂O): Absorbed from the soil by the roots and transported to the leaves.
3. Sunlight: The source of energy, absorbed by the green pigment called Chlorophyll.
4. Chlorophyll: The green pigment present in the leaves that captures sunlight.

The Chemical Equation (The Secret Formula!)

This is the language of scientists. Let's learn it. It's easy!

Raw Materials ----------> Products

Carbon Dioxide + Water ---(Sunlight/Chlorophyll)---> Glucose + Oxygen

Now, let's write it like a proper chemical equation:

6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂

(6 molecules of Carbon Dioxide + 6 molecules of Water → 1 molecule of Glucose + 6 molecules of Oxygen)

Memorization Tip

Remember the phrase: "Cows Drink Water → Grass On" (CO₂ + H₂O → Glucose + O₂). It's silly, but it works!

Numerical & Application 1: The Oxygen Factory

• Scenario: A single large tree like the Neem tree on the Willer Academy ground is estimated to produce approximately 100 kg of oxygen in a year.
• Problem: If an average human being requires about 0.84 kg of oxygen per day to survive, calculate for how many days the oxygen produced by this one tree can support one human.
• Solution:
  • Oxygen produced by the tree per year = 100 kg
  • Oxygen required by a human per day = 0.84 kg
  • Number of days = (Total Oxygen) / (Oxygen per day) = 100 kg / 0.84 kg/day
  • Answer ≈ 119 days

This is why we must plant and protect trees! They are essential for our survival.

Task 2: Experiment Time!

Let's prove sunlight is necessary! Take a potted plant with variegated leaves (like a Croton or Money plant). Cover a part of one leaf with black chart paper. Leave the plant in sunlight for 3-5 days. Then, test that leaf for starch using iodine solution. What do you observe? The covered part will not turn blue-black, proving it did not perform photosynthesis without sunlight!

1.4 Other Ways of Nutrition

Not all plants are self-sufficient. Some have fascinating strategies!

A. Parasitic Plants: Derive food from another living plant (the host).

• Example: Cuscuta (Amarbel). It has a special root-like structure called a haustorium that penetrates the host plant to suck its food.

B. Insectivorous Plants: They grow in soil which is deficient in nutrients like Nitrogen. So, they trap and digest insects to fulfill their nutrient requirement.

• Examples: Pitcher Plant, Venus Flytrap. The Pitcher Plant has a leaf modified into a pitcher with a lid. The inside has digestive juices.

C. Symbiotic Relationship: Some plants live together and share shelter and nutrients. This relationship is called Symbiosis and the plants are called symbionts.

• Example: Lichens. It is an association between an alga and a fungus. The alga prepares food, and the fungus provides water and minerals.

Numerical & Application 2: The Symbiotic Deal

• Scenario: In a lichen, the algal partner is estimated to produce 500 units of energy through photosynthesis.
• Problem: If the algal partner uses 200 units for itself and shares the rest equally with its fungal partner, how many energy units does the fungus receive? If the fungus provides 150 units of water and minerals to the alga, what is the net gain for the alga from this symbiotic relationship?
• Solution:
  1. Energy produced by alga = 500 units
  2. Energy used by alga itself = 200 units
  3. Energy left to share = 500 - 200 = 300 units
  4. Energy shared equally means fungus gets = 300 / 2 = 150 units
  5. Fungus provides water/minerals to alga = 150 units (this is a gain for the alga)
  6. Net gain for alga = (Energy gained from fungus) - (Energy given to fungus) = 150 - 150 = 0 units?

Wait! This seems confusing. The alga already kept 200 units for itself. The sharing is from the surplus. The fungus gets 150 units of food, and in return, the alga gets 150 units of water/minerals. It's a fair trade! Both benefit.

Chapter Summary Mind Map

NUTRITION IN PLANTS

|

|--> Autotrophic (Self-feeding)

| |

| |--> PHOTOSYNTHESIS

| |--> Raw: CO₂ + H₂O

| |--> Conditions: Sunlight + Chlorophyll

| |--> Products: Glucose + O₂

| |--> Equation: 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂

|

|--> Heterotrophic (Dependent)

|

|--> Parasitic (e.g., Cuscuta)

|--> Insectivorous (e.g., Pitcher Plant)

|--> Symbiotic (e.g., Lichens)

Section B: MCQ Challenge (20 Questions)

Test your knowledge and find where you need to improve!

1. The green pigment present in leaves is:

a) Chlorophyll

b) Mitochondria

c) Stomata

d) Chloroplast

2. Which of these is NOT required for photosynthesis?

a) Oxygen

b) Water

c) Carbon Dioxide

d) Sunlight

Answers: 1-a, 2-a, 3-b, 4-c, 5-b, 6-a, 7-d, 8-b, 9-b, 10-a, 11-b, 12-b, 13-b, 14-b, 15-b, 16-b, 17-b, 18-b, 19-b, 20-d

Section C: Answer in Detail (For Answer Writing Practice)

Q1. Describe the process of photosynthesis with a well-labeled diagram of a leaf cross-section showing chloroplasts and stomata.

Hint: Explain all the steps, raw materials, products, and the role of each part. Draw a neat diagram.

Q2. Differentiate with examples between autotrophic and heterotrophic nutrition in plants.

Hint: Make a table with three columns: Basis of Difference, Autotrophic, Heterotrophic. Cover mode, example, and food source.

Q3. Explain with an experiment to show that sunlight is necessary for photosynthesis.

Hint: Describe the variegated leaf experiment step-by-step with your observations and conclusion.

Section D: Tackle These! (Higher Order Thinking Skills - HOTS)

Q1. If you were to set up a greenhouse for growing tomatoes at Willer Academy's lab, what factors would you control to maximize photosynthesis and yield?

Think about: CO₂ levels, water, light duration & intensity, temperature, nutrients.

Q2. A friend tells you, "We should cut down all trees as they respire and release CO₂ at night." How would you, as a Willer Academy student, scientifically convince him otherwise?

Think about: Net oxygen production over 24 hours, the balance of photosynthesis vs. respiration, and other benefits of trees.

Q3. Design a simple model to demonstrate how an insectivorous plant like a pitcher plant traps its prey. What materials would you use?

Think creatively: Use a paper cup for the pitcher, a flap for the lid, and some sticky liquid at the bottom.

"The mightiest oak was once a little nut that held its ground." - Keep learning, keep growing.

Er. Rahul Kumar Dubey Sir

Willer Academy - Building a Stronger Nation, One Student at a Time.