Botany: Eudicot Structure and Growth

Structures in a Typical Eudicot Leaf

• Main photosynthetic organ; intercepts light and exchanges gases with the atmosphere.
• Leaf components:
  • Leaf blade - the flat part for photosynthesis.
  • Leaf veins - contain xylem and phloem for water and nutrient transport.
  • Petiole - the stalk connecting leaf to stem.
  • Stipules - appendages at the base of some petioles.

Plant Tissue Types in Leaves

• Dermal tissue:

  • Cuticle - waxy layer protecting the leaf.
  • Epidermis - outer layer of cells on both sides of leaves.
  • Stomata - openings for gas exchange.

• Vascular tissue:

  • Enclosed in bundle sheath cells, includes xylem and phloem.

• Ground tissue:

  • Mesophyll - where photosynthesis occurs.
    • Palisade mesophyll - upper layer with elongated cells for light capture.
    • Spongy mesophyll - lower layer with loosely arranged cells for gas exchange.

Leaf Types

• Simple leaves - single, undivided blade.
• Compound leaves - blade divided into multiple leaflets.

Specialized Leaf Modifications

• Floral leaves (bracts) - e.g., in poinsettias.
• Spines - e.g., in cacti for defense.
• Reproductive leaves - e.g., in Kalanchoes.
• Insectivorous leaves - e.g., pitcher plants for nutrient acquisition.
• Tendrils - e.g., in climbing vines.
• Storage leaves - e.g., in onion bulbs.

Anatomy of a Stem

• Contains buds, nodes, internodes, and scars from previous leaves.
• Buds contain apical meristems for new stem and leaf production.
• Axillary buds are located at branch and stem angles.
• Internodes are the spaces between nodes.

Structures in Woody Stems

• Pith - central ground tissue in young woody plants.
• Vascular cambium - meristem producing xylem and phloem.
• Cortex - ground tissue between vascular bundles and epidermis.
• Cork cambium - produces cork cells, which replace the epidermis.
• Bark - consists of secondary phloem, cork cambium, and cork.

Differences Between Nonwoody and Woody Stems

• Nonwoody (herbaceous) eudicots have epidermis, cortex, and vascular bundles in a ring with a central pith.
• Woody stems experience secondary growth due to vascular cambium, producing annual rings in wood.
• Cork replaces epidermis; bark protects underlying tissues.

Root Systems

• Roots anchor plants, absorb minerals and water, and store carbohydrates.
• Primary root - first root, lateral roots branch off of it.

Root Tip Zones

• Three zones in eudicot and monocot root tips:
  • Zone of cell division - contains apical meristem and is protected by root cap.
  • Zone of elongation - where cells elongate and begin differentiation.
  • Zone of maturation - where root hairs develop for nutrient absorption.

Vascular Tissue Arrangement in Roots

• Eudicot roots have xylem arranged in a star shape with phloem located between the arms.
• Monocot roots have a central pith surrounded by vascular tissue with alternating xylem and phloem bundles.
• Endodermis - regulates mineral entry into vascular tissue.