Detailed Notes on Plant Anatomy and Physiology

Plants General Anatomy & Physiology

Cell Types and Tissues

  • Cell Types: Different cell types within plants contribute to various functions, e.g.:
    • Parenchyma: Involved in storage and photosynthesis.
    • Collenchyma: Provides flexible support to growing parts of the plant.
    • Sclerenchyma: Offers rigid support and protection.
  • Tissues:
    • Dermal Tissue: Protective outer layer.
    • Vascular Tissue: Includes xylem (water transport) and phloem (nutrient transport).
    • Ground Tissue: Functions in photosynthesis, storage, and support.

Plant Organs

  • Roots: Absorb water and nutrients, anchor the plant.
  • Stems: Support leaves, transport materials.
  • Leaves: Main site of photosynthesis.

Variation Across Major Plant Taxa

  • Green Algae: Aquatic, photosynthesize similar to plants.
  • Bryophytes: Non-vascular plants like mosses, dependent on water for reproduction.
  • Angiosperms: Flowering plants, significant in terrestrial ecosystems.

Reproduction

  • Alternation of Generations: Lifecycle includes both haploid (gametophyte) and diploid (sporophyte) stages.

Early Embryonic Development

  • Involves formation of structures leading to germination and subsequent growth.
  • Requires nutrient supply from seeds until development of photosynthetic tissues.

Growth & Responding to Environment

  • Primary Growth: Involves elongation of shoots and roots; occurs at apical meristems.
  • Secondary Growth: Thickening of stems and roots, involves vascular cambium.
  • Environmental Response:
    • Light and Germination: Sensing light activates growth responses (phototropism).
    • Hormonal Influence: Auxins and gibberellins playing significant roles.
  • Acid-Growth Hypothesis: Acidic conditions promote cell elongation by loosening cell walls.
  • Apical Dominance: Primary shoot growth is favored over lateral shoots, regulated by hormones like auxins.

Secondary Compounds

  • These are often produced to deter herbivory or attract pollinators.

Transport in Plants

Xylem

  • Anatomy and Function: Conducts water and soluble minerals; comprised of tracheids and vessel elements.
  • Mechanisms of Water Transport:
    • Capillary Action: Movement through microscopic veins.
    • Root Pressure: Generated in roots due to osmotic pressure.
    • Transpiration-Cohesion-Tension Hypothesis: Explains movement of water from roots to leaves.

Phloem

  • Anatomy and Structure: Transports sugars produced during photosynthesis through sieve-tube elements and companion cells.
  • Transport Mechanism:
    • Pressure-Flow Hypothesis: Explains the movement of sap through phloem.

Nutrients Overview

  • Nutrients: Essential for plant health; include macro and micronutrients.
  • Consequences of Local Depletion: Affects growth and overall health of plants.

Absorption Mechanisms

  • Root Hairs: Increase surface area for absorption of water and nutrients.
  • Casparian Strip: Prevents passive flow of substances, forces active transport into vascular bundles.
  • Symbiotic Relationships:
    • Fungi/Mycorrhizae: Enhance nutrient uptake.
    • Rhizobia/Root Nodules: Allow nitrogen fixation in legumes.

Special Adaptations

  • Some plants develop adaptations to thrive in specific environments, e.g. desert plants conserve water, aquatic plants adjust to buoyancy.