Chapter 1: Nutrition in Plants
1.1 Mode of Nutrition in Plants
Nutrients and Nutrition
- Nutrients: Components of food like carbohydrates, proteins, fats, vitamins, and minerals necessary for the body.
- Nutrition: The mode of taking food by an organism and its utilisation by the body.
Autotrophs vs Heterotrophs
- Autotrophic Nutrition: Mode where organisms make food themselves from simple substances (e.g., plants). Organisms are called autotrophs.
- Heterotrophs: Organisms (animals and humans) that depend on food prepared by plants.
1.2 Photosynthesis — Food Making Process in Plants
The Mechanism of Photosynthesis
- Leaves: The food factories of plants where food synthesis occurs.
- Stomata: Tiny pores on the leaf surface surrounded by guard cells used for gas exchange ($CO_2$ intake).
- Chlorophyll: Green pigment in leaves that captures solar energy.
- Photosynthesis Equation: Carbon dioxide + Water in the presence of Sunlight and Chlorophyll yields Carbohydrate + Oxygen.
- Starch: A carbohydrate whose presence in leaves indicates that photosynthesis has occurred.
Cell Structure
- Cells: Tiny units that make up the bodies of living organisms.
- Cell Membrane: Thin outer boundary enclosing the cell.
- Nucleus: Centrally located, spherical structure in a cell.
- Cytoplasm: Jelly-like substance surrounding the nucleus.
Synthesis of Other Nutrients
- Carbohydrates contain Carbon, Hydrogen, and Oxygen, used to synthesise proteins and fats.
- Proteins require nitrogen. Plants obtain nitrogen from the soil where Rhizobium bacteria convert gaseous nitrogen into a usable soluble form.
1.3 Other Modes of Nutrition in Plants
Parasitic Plants
- Cuscuta (Amarbel): A non-green plant that climbs on a host plant to derive readymade food, acting as a parasite.
Insectivorous Plants
- Insectivorous Plants: Insect-eating plants (e.g., Pitcher plant) that trap and digest insects using specialized leaf structures to fulfill nutrient requirements.
1.4 Saprotrophs and Symbiosis
Saprotrophic Nutrition
- Saprotrophic Nutrition: Mode of nutrition where organisms take in nutrients from dead and decaying matter.
- Saprotrophs: Organisms like fungi that use saprotrophic nutrition.
Symbiosis
- Symbiosis: A relationship where two organisms live together and share shelter and nutrients.
- Lichens: A symbiotic partnership between a chlorophyll-containing alga and a fungus.
1.5 How Nutrients are Replenished in the Soil
Soil Enrichment
- Nutrients like nitrogen, potassium, and phosphorus are replenished using manures and fertilizers.
- Rhizobium bacteria live in the root nodules of leguminous plants (peas, gram, moong) to fix atmospheric nitrogen, sharing a symbiotic relationship.