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:
Root cap
Zone of cell division
Zone of elongation
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.