Plant Nutrition and Interaction with Environment

Important Focus Points

• Types of nutrients critical to plants and their roles.
• Impact of changes in nutrient availability on plants.
• Role of microbes in nutrient availability for plants.

Essential Inorganic Nutrients

• 17 essential elements are necessary for plant growth and reproduction.
  • Macronutrients: Required in large amounts (9 total)
  • Micronutrients: Required in smaller amounts (8 total)
• Both macronutrients and micronutrients are vital for plant functions.

Macronutrients

• Constituents of plant weight (99.7%)
  • Carbon (C) - Integral part of organic compounds
  • Oxygen (O) - Integral part of organic compounds
  • Hydrogen (H) - Integral part of organic compounds
  • Nitrogen (N) - 45% of plant weight, crucial for proteins and nucleic acids
  • Potassium (K) - Regulates stomatal movement
  • Calcium (Ca) - Cell wall component, maintains membrane structure
  • Magnesium (Mg) - Component of chlorophyll
  • Phosphorus (P) - Nucleic acids, ATP
  • Sulfur (S) - Component of proteins

Micronutrients

• Needed in tiny quantities (0.3% of plant weight)
  • Molybdenum (Mo)
  • Iron (Fe) - Component of proteins in electron transport chains
  • Manganese (Mn)
  • Boron (B)
  • Zinc (Zn)
  • Copper (Cu)
  • Chlorine (Cl)
  • Nickel (Ni)
  • Sodium (Na) - Required by some plants only

Fertilizers

• Nutrient availability in soil is critical for plant health.
• Common nutrient deficiencies:
  • Nitrogen deficiency (most common)
  • Phosphorus deficiency (second most common)
• Fertilizer types:
  • Inorganic chemical fertilizers
  • Organic compost
• Fertilizers help alleviate nutrient deficiencies.

Soil Conservation

• Cultivation practices can degrade soil health.
  • Irrigation can increase salinity.
  • Erosion from plowed lands can remove topsoil.
  • Chemical fertilizers can contaminate groundwater.
• Good soil management practices:
  • Water-conserving irrigation
  • Erosion control measures
  • Prudent use of fertilizers and herbicides.

Role of Microbes in Plant Nutrition

• Most plants depend on soil bacteria for nitrogen supply.
  • Nitrogen in the atmosphere (N2) cannot be directly absorbed.
  • Nitrogen-fixing bacteria convert atmospheric N2 to ammonia (NH3).
  • Ammonifying bacteria decompose organic matter to supply ammonium (NH4+).
  • Nitrifying bacteria convert ammonium to nitrates (NO3-), the form plants uptake.

Symbiotic Relationships

• Plants often form symbioses with fungi (mycorrhizae):
  • Increase root area for absorption.
  • Aid in absorbing phosphates and minerals.
  • Release growth factors and antibiotics.
• Leguminous plants (e.g., peas, beans) form root nodules with nitrogen-fixing bacteria (Rhizobium):
  • These associations lead to nitrogen richness in plants.

Parasitic and Carnivorous Plants

• Some plants may evolve to become:
  • Parasitic (e.g., mistletoe): Absorb nutrients from host plants.
  • Carnivorous (e.g., sundew, Venus flytrap): Capture insects for nutrients in poor soil.
  • Epiphytes (e.g., orchids): Grow on other plants to absorb water and minerals.

Summary

• Importance of understanding plant nutrients, their availability, microbial interactions, and adaptations in diverse environments.