By Subhash Kumar | Science Educator | UREducator
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Nutrition in Plants
Complete Teaching Resource for CBSE Class 7 Science Chapter 1
Class: VII
Subject: Science
Chapter: 1
Duration: 4 Hours
What Students Will Achieve
Knowledge
- Define nutrition and explain its importance
- Describe the process of photosynthesis
- Differentiate between autotrophs and heterotrophs
- Identify different modes of nutrition in plants
Understanding
- Explain why photosynthesis is vital for life on Earth
- Analyze how parasitic plants obtain nutrition
- Understand symbiotic relationships in nature
- Explain how nutrients are replenished in soil
Skills
- Conduct experiments to demonstrate photosynthesis
- Test leaves for starch presence
- Observe different plant nutrition modes
- Create models of plant nutrition processes
Prior Knowledge Assessment
Starter Questions:
- Why are plants called the primary producers in a food chain?
- What gas do plants release during photosynthesis?
- How do non-green plants like fungi obtain their nutrition?
The Food Making Process in Plants
Key Requirements for Photosynthesis
Sunlight
Provides energy for the chemical reaction
- Captured by chlorophyll in chloroplasts
- Energy converted from solar to chemical
Water
Absorbed by roots from soil
- Transported through xylem vessels
- Provides hydrogen atoms for glucose
Carbon Dioxide
Enters through stomata in leaves
- Provides carbon and oxygen atoms
- Regulated by guard cells
Photosynthesis Equation
Chemical Reaction
6CO2 + 6H2O + Light Energy → C6H12O6 + 6O2
Carbon Dioxide + Water + Sunlight → Glucose + Oxygen
Importance of Photosynthesis
| Benefit | Explanation |
|---|---|
| Food Production | Base of all food chains - produces glucose that forms complex foods |
| Oxygen Supply | Releases oxygen essential for respiration of most organisms |
| Carbon Cycle | Helps regulate atmospheric CO2 levels |
| Energy Flow | Converts solar energy into chemical energy stored in food |
Experiment: Testing for Starch in Leaves
Objective: Demonstrate that photosynthesis produces starch
- Take a potted plant with broad leaves
- Keep in dark for 72 hours to destarch
- Expose to sunlight for 6 hours
- Boil leaf in water to soften it
- Place in alcohol to remove chlorophyll
- Add iodine solution - blue-black color indicates starch
Different Ways Plants Obtain Nutrition
Types of Plant Nutrition
Autotrophic
(Self-feeding)
- Make own food through photosynthesis
- Example: Green plants, algae
- Contain chlorophyll
Parasitic
(Dependent on host)
- Lack chlorophyll, depend on host plants
- Example: Cuscuta (Dodder), Rafflesia
- Harm host by taking nutrients
Insectivorous
(Insect-eating)
- Grow in nitrogen-deficient soils
- Example: Pitcher plant, Venus flytrap
- Digest insects for nitrogen
Saprotrophic
(Decomposers)
- Feed on dead and decaying matter
- Example: Fungi, mushrooms
- Secrete digestive enzymes
Symbiotic Relationships
| Relationship | Partners | Benefits |
|---|---|---|
| Lichens | Fungus + Alga | Fungus provides shelter, alga provides food |
| Rhizobium | Bacteria + Legumes | Bacteria fixes nitrogen, plant provides shelter |
| Mycorrhizae | Fungus + Plant roots | Fungus helps absorb nutrients, gets carbohydrates |
Activity: Observing Fungal Growth
Objective: Demonstrate saprotrophic nutrition
- Take a slice of bread and moisten it
- Keep in warm, dark place for 2-3 days
- Observe fluffy fungal growth under magnifying glass
- Note color, texture and pattern of growth
- Research what conditions promote fastest growth
Replenishing Nutrients in Soil
Methods of Nutrient Replenishment
Fertilizers
- Chemical compounds rich in N, P, K
- Quickly absorbed by plants
- Can cause soil/water pollution if overused
Manure
- Organic matter from plant/animal waste
- Improves soil structure and water retention
- Slow release of nutrients
Nitrogen Fixation
- Rhizobium bacteria in legume root nodules
- Convert atmospheric N2 to usable forms
- Natural alternative to nitrogen fertilizers
Crop Rotation Benefits
| Practice | Benefit | Example |
|---|---|---|
| Legume Rotation | Replenishes soil nitrogen naturally | Wheat after peas/beans |
| Deep-rooted Crops | Brings up deep nutrients | Alfalfa after corn |
| Pest Control | Breaks pest/disease cycles | Alternating plant families |
Project: Comparing Plant Growth
Objective: Demonstrate effect of nutrients on plant growth
- Plant seeds in 3 pots with different soils
- Pot 1: Normal garden soil (control)
- Pot 2: Soil with added fertilizer
- Pot 3: Soil depleted of nutrients
- Measure growth over 2-3 weeks
- Compare leaf color, stem height, overall health
Evaluation Strategies
Formative Assessments
- Photosynthesis diagram labeling
- Modes of nutrition matching quiz
- Experiment report evaluation
- Classroom participation in discussions
Summative Assessments
- Chapter test (MCQs + short answer)
- Practical exam on starch test
- Project presentation on plant nutrition
- Case study on importance of photosynthesis
Extended Learning: Visit a Farm or Nursery
Objective: Observe practical applications of plant nutrition concepts
- Interview farmers about soil management practices
- Identify different fertilizers/manures used
- Observe leguminous crops and root nodules
- Learn about organic farming techniques
- Prepare a report with photographs
Frequently Asked Questions
Why are some plants like Cuscuta yellow instead of green?
Cuscuta (Dodder) appears yellow because:
- It lacks chlorophyll, the green pigment needed for photosynthesis
- As a parasitic plant, it doesn't need to make its own food
- It obtains all nutrients from the host plant it grows on
- The yellow color comes from other pigments present
How can non-green plants like fungi survive without photosynthesis?
Fungi use different nutrition strategies:
- Saprotrophic nutrition: Feed on dead and decaying organic matter
- Parasitic nutrition: Derive nutrients from living hosts
- Symbiotic relationships: Partner with other organisms (like in lichens)
- They secrete digestive enzymes to break down complex food externally
