Learning Objectives
- Understand the mode of nutrition in plants
- Learn the process of photosynthesis
- Know about other modes of nutrition in plants
- Understand how nutrients are replenished in the soil
Key Concepts
Autotrophic Nutrition
Autotrophs: Organisms that can make their own food from simple substances like carbon dioxide and water are called autotrophs. Green plants are autotrophs.
Photosynthesis: The process by which green plants make food using sunlight, carbon dioxide, and water.
Equation: Carbon dioxide + Water → (Sunlight + Chlorophyll) → Glucose + Oxygen
6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂
Conditions for Photosynthesis
- Sunlight: Provides energy for the reaction
- Chlorophyll: Green pigment in leaves that captures sunlight
- Carbon dioxide: Enters through stomata on leaf surface
- Water: Absorbed by roots from the soil
Other Modes of Nutrition
Parasitic plants: Cuscuta (Amarbel) derives nutrition from the host plant.
Insectivorous plants: Venus flytrap and pitcher plant trap and digest insects for nitrogen.
Saprotrophic nutrition: Fungi like mushrooms feed on dead and decaying organic matter.
Symbiotic relationship: Lichens (algae + fungi) and Rhizobium bacteria in legume root nodules.
Replenishment of Nutrients in Soil
Farmers use fertilizers and manure. Crop rotation with leguminous plants helps fix atmospheric nitrogen through Rhizobium bacteria.
Summary
Plants make their own food by photosynthesis using sunlight, carbon dioxide, water, and chlorophyll. Some plants are parasites, insectivorous, or saprotrophic. Symbiotic relationships like lichens and Rhizobium help in mutual nutrition. Nutrients in soil are replenished by fertilizers, manure, and nitrogen-fixing bacteria.
Important Terms
- Autotroph: Organism that makes its own food
- Heterotroph: Organism that depends on others for food
- Photosynthesis: Process of making food using sunlight
- Chlorophyll: Green pigment that traps sunlight
- Stomata: Tiny pores on leaf surface for gas exchange
- Parasite: Organism that lives on/in a host and derives nutrition
- Saprotroph: Organism that feeds on dead matter
- Symbiosis: Mutually beneficial relationship between organisms
Quick Revision
- Green plants = Autotrophs (make own food)
- Photosynthesis needs: Sunlight + CO₂ + H₂O + Chlorophyll
- Stomata: pores for CO₂ entry
- Cuscuta = Parasite, Mushroom = Saprotroph
- Rhizobium fixes nitrogen in legume roots