In Depth Notes on Plant Form and Physiology

Chapter 30: Plant Form and Physiology of Angiosperms (Phylum Anthophyta)

  • Angiosperms are divided into two major groups: Dicots (Eudicots) and Monocots.
    • Approximately 25% of all angiosperms are monocots, while about 60% are dicots.
    • Key features include differences in floral parts and seed structure.

Dicot Characteristics

  • Dicot seeds have:
    • Two cotyledons (seed leaves).
    • Floral parts typically occur in fours or fives or multiples thereof.
    • Vascular bundles are arranged in a ring within the stem.
    • Leaf veins are usually netlike.
    • Pollen grains generally have three pores or furrows.

Monocot Characteristics

  • Monocot seeds have:
    • One cotyledon.
    • Floral parts typically occur in threes or multiples thereof.
    • Vascular bundles are distributed throughout the ground tissue of the stem.
    • Leaf veins are usually parallel.
    • Pollen grains generally have one pore or furrow.

Plant Organization

  • Plants have a hierarchy of organization:
    • Organ: A structure made up of different tissues to perform specific functions (e.g., roots, stems, leaves).
    • Tissue: A group of cells working together, categorized into three main types: dermal, vascular, and ground.

Plant Organs

Roots

  • Tap Root: Main vertical root.
  • Lateral Roots: Secondary roots that anchor the plant.
  • Root Hairs: Extensions increasing surface area for water and nutrient absorption.
  • Types of Roots Include:
    • Prop roots, storage roots, strangling aerial roots, buttress roots, and pneumatophores.

Stems

  • Stems support leaves and reproductive structures, facilitating movement of nutrients and water.
  • Key Structures Include:
    • Nodes: Points of attachment for leaves.
    • Internodes: Segments between nodes.
    • Apical Bud: Located at the shoot tip, promoting elongation (apical dominance).

Leaves

  • Main site of photosynthesis, consisting of a flat blade and a petiole.
  • Example: Amazonian water lily is recognized for its large leaf size.
  • Modified Leaves: Some leaves take on specialized functions like storage or reproduction.

Plant Tissues

Dermal Tissue

  • Function: Protects the plant and controls gas, water, and nutrient flow.
    • Epidermis: The outer layer of cells.
    • Cuticle: A protective layer preventing water loss.

Vascular Tissue

  • Responsible for transportation within the plant:
    • Phloem: Transports sugars.
    • Xylem: Transports water and minerals.

Ground Tissue

  • This tissue comprises the majority of the plant body, providing support, storage, and performing photosynthesis.
  • Components:
    • Pith: Center of stems.
    • Cortex: Outer layer of ground tissue.
  • Types of Cells:
    • Parenchyma: Thin-walled and flexible; involved in storage and metabolism.
    • Collenchyma: Thick cell walls provide structural support.
    • Sclerenchyma: Rigid due to thick walls; usually dead at maturity with two subtypes: sclereids (short, irregular) and fibers (long, slender).

Meristems

  • Definition: Regions of undifferentiated cells that can divide and specialize.
  • Types:
    • Apical Meristems: Located at root and shoot tips, allowing primary growth.
    • Lateral Meristems: Contribute to secondary growth (thickening).

Secondary Growth

  • Vascular Cambium: Produces more xylem and phloem.
  • Cork Cambium: Replaces epidermis with a protective periderm.

Organ and Tissue Organization

  • Roots: Recognized by features like endodermis (innermost cell layer) and pericycle (outermost layer in vascular tissue).
  • Stems: Identify between monocot and dicot based on vascular bundle arrangement.
  • Leaves: Stomata adapt for gas exchange, surrounded by guard cells.

Key Vocabulary

  • Phylum Anthophyta, Dicot, Monocot, Organ, Tissue, Root system, Shoot system, Tap Root, Lateral Root, Stem, Leaf, Dermal Tissue, Epidermis, Cuticle, Vascular Tissue, Phloem, Xylem, Ground Tissue, Meristems, Apical Meristems, Lateral Meristems, Endodermis, Stomata.

Review Questions to Consider

  1. What are the defining traits of dicots versus monocots?
  2. Describe the primary functions of roots, stems, and leaves.
  3. Explain apical dominance.
  4. What is the connection between the three types of plant tissues?
  5. Identify the major plant cell types and their functions.