#7 - Plant Structure and Function

Overview of Plant Structure and Function

A comprehensive look into the anatomy and physiology of plants, exploring their successful adaptation as life forms.

Key Concepts in Plant Physiology

  • Introduction to Plant Physiology:
    • Key Components: Cells, Tissues, Organs
    • Areas of Focus:
    • Vascular transport
    • Photosynthesis
    • Plant metabolism and growth

Fundamental Questions

  • Why are plants successful?
    • Comparison with animals:
    • Plants: Photoautotrophic, chlorophyll, continuous growth (indeterminate), rooted, have rigid cell walls.
    • Animals: Chemoheterotrophic, no chlorophyll, limited growth (determinate), free-moving, lack rigid cell walls.
    • Emphasizes the unique characteristics of plant cells:
    • Live in rigid structures (cell walls)

Evolution of Plants

  • Ancestral Green Alga: Origin of land plants ~470 million years ago.

  • Non-Vascular Plants: Examples include mosses and liverworts, which emerged around 425 million years ago.

  • Vascular Plants:

    • Evolution of vascular plants around 425 mya.
    • Types: Lycophytes, Monilophytes

  • Seed Plants: Gymnosperms (360 mya) and Angiosperms (most diverse)

Angiosperm Groups

  • Monocots vs. Eudicots:
    • Monocots: One cotyledon, parallel veins, fibrous root system, flower parts in threes.
    • Eudicots: Two cotyledons, branched veins, taproot system, floral parts in multiples of four or five.

Plant Tissues Overview

Types of Plant Tissues
  1. Simple Tissues
    • Parenchyma: Versatile; performs photosynthesis, storage, and wound repair. Alive at maturity.
    • Collenchyma: Provides flexible support; alive at maturity with unevenly thickened cell walls.
    • Sclerenchyma: Provides rigid support; contains fibers and sclereids, dead at maturity.
Complex Tissues

  • Xylem:

    • Composed of parenchyma (alive), sclerenchyma (dead), and tracheary elements (water/mineral transport; passive):
    • Tracheids: Long, thin, water moves through pits.
    • Vessel Elements: Wider, aligned end to end for efficient water transport.

  • Phloem:

    • Composed of living sieve elements (transport organic compounds), parenchyma (-loading/unloading), and sclerenchyma (support).
    • Sieve Elements: Sieve-tube in angiosperms - alive but lack a nucleus, paired with companion cells.

Tissue Systems

  • Dermal Tissue: Protective covering (epidermis), includes periderm (bark).
  • Ground Tissue: Comprises parenchyma, collenchyma, and sclerenchyma; performs photosynthesis, storage, and support.
  • Vascular Tissue:
    • Xylem & Phloem, responsible for the transport of water, nutrients, and sugars.

Organs of the Plant

  1. Roots: Anchors the plant, absorbs nutrients and water.
    • Various modifications: storage, aerial roots, pneumatophores.
  2. Stems: Supports leaves; responsible for transport between roots and leaves.
  3. Leaves: Main site of photosynthesis, may have various adaptations (e.g., cuticle, stomata).
  4. Reproductive Organs: Involved in reproduction (flowers and seeds).

Growth Patterns

  • Apical Meristem: At the tips of roots/shoots leads to primary growth.
  • Lateral Growth: Involves cambium for secondary growth (thickening).

Plant Adaptations and Functions

  • Root Hairs: Increase the surface area for absorption of water and nutrients.
  • Tissue Modification: Adaptations critical for survival in different environments.

Conclusion

  • Understanding plant structure and function is essential for appreciating their role in ecosystems and their adaptability as a terrestrial organism.