6, Plant Form Notes

Plant Form Overview

• Chapter 35 Topics: Includes Gymnosperms, Angiosperms, Ginkgo, Gnetophytes, Conifers, Cycads, Archaefructus (extinct), Amborella, Water lilies, Monocots, Magnoliids, Eudicots, Staranis.

Organization of the Plant Body

• A vascular plant consists of two main systems:
  • Root System:
  • Anchors the plant.
  • Absorbs water and ions from the soil.
  • Shoot System:
  • Comprises supporting stems, photosynthetic leaves, and reproductive flowers.
  • Made up of repetitive units: internode, node, leaf, axillary bud.

Plant Cell Types

• Plant cells are distinguished by:
  • Size of vacuoles.
  • Living or not at maturity.
  • Thickness of secretions in cellulose cell walls:
  • Some have only a primary cell wall of cellulose.
  • Others may have secondary cell walls reinforced with lignin.

Meristem and Cell Division

• Meristems are:
  • Located at the tips of stems and roots.
  • Responsible for extension of shoots and roots through apical meristems.
  • Produce hormones that repress the development of lateral buds.
• Meristems differentiate into specialized cells that do not divide further after maturation.

Plant Tissues

• Three main types of plant tissue:
  • Dermal Tissue:
  • Forms the outer protective covering (epidermis).
  • One cell layer thick, covered by a fatty cuticle.
  • Ground Tissue:
  • Includes three cell types:
    • Parenchyma: storage and photosynthesis.
    • Collenchyma: support and protection.
    • Sclerenchyma: provide additional support.
  • Vascular Tissue:
  • Xylem: Conducts water and dissolved minerals.
  • Phloem: Transports carbohydrates and other essential substances for growth.

Roots

• Function: Anchoring and Absorption
• Four recognized regions of root structure:
  1. Root cap
  2. Zone of cell division
  3. Zone of elongation
  4. Zone of maturation
• Types of root systems:
  • Taproot System: Single large root with small branches.
  • Fibrous Root System: Many roots with similar diameter.
• Some plants produce modified or adventitious roots.

Stems

• Functions of stems:
  • Provide support to above-ground organs.
  • Undergo growth via apical and lateral meristems.
• Phyllotaxy (arrangement of leaves) can be:
  • Whorled, Opposite, or Alternate.
• Vascular tissue organization distinguishes monocots from eudicots:
  • Monocot: Scattered vascular bundles.
  • Eudicot: Vascular bundles arranged in a ring.

Leaves

• Function: Primary site for photosynthesis.
• Structure initiated as primordia by apical meristems.
• Comprised of differentiated parts including the blade and petiole.
• Leaf veins differ between monocots and eudicots:
  • Monocots often have parallel veins.
  • Eudicots have an intricate network of veins.
• Stomata: Openings in leaf epidermis for gas exchange, regulated by guard cells.

Summary of Monocots vs Eudicots

• Monocots:
  • Flower parts in multiples of three.
  • Vascular bundles scattered in stems.
  • Parallel leaf veins.
• Eudicots:
  • Flower parts in fours or fives.
  • Vascular bundles form a ring in stems.
  • Network pattern of leaf veins.

Conclusion

• The plant form is complex and diverse, with specialized structures for growth, support, and function. Understanding these components is crucial for comprehending plant biology.