Medicinal Plants Lecture 5: Plant Anatomy

Lecture 5 - Medicinal Plants

• Lecture by Dr. Amal F. Soliman (Associate Professor of Pharmacognosy) and Dr. Walaa Safwat (Lecturer of Pharmacognosy), 2024/2025 academic year.
• Topics covered include plant anatomy, focusing on transverse sections (TS) of roots, stems, and leaves.

Plant Anatomy: Transverse Sections (TS)

• Root TS:

  • Casparian strips are present in the endodermis and are located on the radial walls.
  • Vascular bundles are arranged radially in roots.

• Stem TS:

  • Dicot stem: Vascular bundles arranged in a single ring; cortex, pith, pericycle, endodermis are distinct. Hypodermis mostly collenchyma.
  • Monocot stem: Many vascular bundles scattered throughout ground tissue; cortex, pith, pericycle, endodermis indistinct. Hypodermis mostly sclerenchyma.

Plant Organs and Their Functions

• Leaves: The primary photosynthetic organs of the plant.
• Stems: Support the plant, transport nutrients, and protect against predators and diseases.
• Roots: Absorb water and nutrients, anchor the plant, and protect from soil bacteria and fungi.

Leaf Anatomy

• Dicot Leaf:
  • Typically have a reticulate venation pattern (net-like veins).
  • Upper epidermis, palisade mesophyll, spongy mesophyll, lower epidermis, vascular bundles (xylem/phloem), and stomata are present.
• Monocot Leaf:
  • Usually have parallel venation (veins running parallel).
  • Arrangement of mesophyll tissues, stomata, and vascular bundles differ from dicots.

Leaf Tissue Summary

• Palisade mesophyll: Located perpendicular to the epidermis, formed of one or more layers of elongated cells; abundant chloroplasts.
• Spongy mesophyll: Irregularly shaped cells (scattered); intercellular spaces are wide aiding gas exchange; fewer chloroplasts.

Leaf Types – Monocot vs. Dicot

• Stomata:

  • Dicot: Stomata are typically polygonal or polyhedral
  • Monocot: Stomata are usually elongated.

• Vascular bundles (V.B.):

  • Dicot: Open or bicollateral.
  • Monocot: Closed collateral.

• Leaf venation:

  • Dicot: Reticulate venation (net-like)
  • Monocot: Parallel venation (parallel veins)

• Additional features: Leaf Structure (cuticle, epidermis, mesophyll, vascular bundles, stomata, etc.), Respiratory cavities/Sub-stomatal chambers.

Dive into Lecture 5 on medicinal plants, focusing on the intricate plant anatomy through transverse sections (TS) of roots, stems, and leaves. This session elaborates on the distinct vascular arrangements and functions of various plant organs essential for understanding pharmacognosy.