Plant Physiology Overview

Plant Physiology

Definition: Study of the functions and processes of plants.
Key Processes:
- Photosynthesis:
  - Conversion of light energy into chemical energy.
  - Occurs in chloroplasts using chlorophyll.
  - Equation: 6CO₂ + 6H₂O + light energy → C₆H₁₂O₆ + 6O₂.
- Respiration:
  - Process of breaking down glucose to release energy.
  - Formula: C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + energy (ATP).
- Transpiration:
  - Evaporation of water from plant surfaces, mainly leaves.
  - Helps in nutrient transport and temperature regulation.
Growth and Development:
- Meristems:
  - Regions of actively dividing cells.
  - Types: Apical (lengthening), Lateral (thickening).
- Hormones:
  - Auxins: Promote cell elongation and root growth.
  - Gibberellins: Stimulate seed germination and stem growth.
  - Cytokinins: Promote cell division and delay aging.
  - Abscisic Acid: Inhibits growth, involved in stress responses.
  - Ethylene: Regulates fruit ripening and flower wilting.
Nutrient Uptake:
- Essential Elements: Macronutrients (N, P, K) and Micronutrients (Fe, Mn, Zn).
- Soil Interaction: Roots absorb water and nutrients; mycorrhizal fungi enhance uptake.
Water Relations:
- Osmosis: Movement of water through a semipermeable membrane.
- Turgor Pressure: Pressure from water inside the cell, maintaining plant structure.
Gas Exchange:
- Stomata: Pores on leaves facilitating gas exchange (CO₂ in, O₂ out).
- Cuticle: Waxy layer minimizing water loss.
Adaptations:
- C4 and CAM Photosynthesis: Adaptations for water conservation and efficiency in arid conditions.
- Hydrophytes: Plants adapted to grow in water; have specialized structures for buoyancy and gas exchange.
Responses to Environment:
- Phototropism: Growth towards light.
- Gravitropism: Growth direction in response to gravity.
- Thigmotropism: Response to touch (e.g., climbing plants).
Plant Defense Mechanisms:
- Physical barriers (thorns, trichomes).
- Chemical defenses (secondary metabolites like alkaloids, tannins).

These concepts form the foundation of plant physiology, illustrating how plants interact with their environment, grow, and function at a cellular and systemic level.

Plant Physiology Overview

Study of the functions and processes that govern plant life, including growth, metabolism, and responses to environmental stimuli.

Key Processes

Photosynthesis:
- Converts light energy into chemical energy within chloroplasts containing chlorophyll.
- Key equation: 6CO₂ + 6H₂O + light energy → C₆H₁₂O₆ + 6O₂.
Respiration:
- Involves breaking down glucose to release energy, primarily for cellular functions.
- Key equation: C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + energy (ATP).
Transpiration:
- The process of water evaporation from plant surfaces, especially leaves, crucial for nutrient transport and temperature control.

Growth and Development

Meristems:
- Areas of active cell division; responsible for plant growth.
- Two types: Apical meristems (lengthening) and Lateral meristems (thickening).
Hormones:
- Auxins: Promote cell elongation and root development.
- Gibberellins: Stimulate seed germination and elongation of stems.
- Cytokinins: Encourage cell division and delay senescence (aging).
- Abscisic Acid: Inhibits growth; plays a role in stress response.
- Ethylene: Influences fruit ripening and flower wilting.

Nutrient Uptake

Essential Elements:
- Macronutrients include Nitrogen (N), Phosphorus (P), and Potassium (K); Micronutrients involve Iron (Fe), Manganese (Mn), and Zinc (Zn).
Soil Interaction:
- Roots are responsible for water and nutrient absorption; mycorrhizal fungi can improve nutrient uptake efficiency.

Water Relations

Osmosis:
- The process of water movement through a semipermeable membrane, critical for maintaining hydration in plants.
Turgor Pressure:
- Internal pressure from water in plant cells, which supports plant structure and rigidity.

Gas Exchange

Stomata:
- Small pores on leaf surfaces that regulate the exchange of CO₂ (intake) and O₂ (release).
Cuticle:
- A waxy layer on leaves that reduces water loss, protecting against desiccation.

Adaptations

C4 and CAM Photosynthesis:
- Specialized methods in plants for maximizing water conservation and photosynthetic efficiency, particularly in arid regions.
Hydrophytes:
- Aquatic plants with adaptations like buoyant structures and specialized gas exchange systems.

Responses to Environment

Phototropism:
- Growth response of plants towards light, optimizing photosynthesis.
Gravitropism:
- Directional growth based on gravity, helping roots grow downwards and shoots upwards.
Thigmotropism:
- Growth in response to touch, notably seen in climbing plants.

Plant Defense Mechanisms

Physical Barriers:
- Structures like thorns and trichomes deter herbivores and provide protection.
Chemical Defenses:
- Production of secondary metabolites (e.g., alkaloids and tannins) to repel pests and pathogens.