Fundamentals of Vascular Plant Anatomy and Classification

BOT 102: General Botany

Course Unit: 3 Compulsory Course Units

Plant Systems

Plants are generally divided into two main systems:

1. Root system: Supports the plant and absorbs water and minerals, typically found underground.
2. Shoot system: Grows above ground and consists of two portions:
   • Vegetative (non-reproductive) parts: Leaves and stems.
   • Reproductive parts: Flowers and fruits.

   The shoot system absorbs light needed for photosynthesis.

(Refer to the plant diagram on page 3 for visual representation of plant parts and systems.)

Differences Between Monocotyledon and Dicotyledon

Flower Symmetry Definitions:

• Trimerous symmetry: An arrangement of flower parts (petals, sepals, stamens) in sets of three.
• Pentamerous symmetry: An arrangement of flower parts (petals, sepals, stamens) in sets of five.

(Refer to page 7 for a diagram illustrating Monocot and Dicot seeds.)

Types of Roots

In flowering plants, there are three main types of roots:

1. Tap roots
2. Fibrous roots
3. Adventitious roots

Venation in Flowering Plants

Venation refers to the pattern of veins on a leaf. There are two main types:

1. Parallel venation: Veins run parallel to each other.
2. Reticulate venation: Veins form a net-like pattern.

(Refer to page 10 for diagrams illustrating monocot and dicot stem cross-sections showing vascular bundle arrangements.)

Plants that have Vascular Tissues (Tracheophytes)

Tracheophytes are vascular plants that possess special vascular tissue arranged in long, discrete strands called vascular bundles. The vascular tissue involves:

• Xylem: Transports water and dissolved minerals from roots to other parts of the plant; also provides structural support.
• Phloem: Transports food (sugars like sucrose) produced during photosynthesis from leaves to other parts, including roots, flowers, and fruits.

Vascular plants typically have stems, leaves, roots, flowers, or seeds. Examples include trees, shrubs, grasses, flowering plants, and ferns.

Categories of Vascular Plants:

• Seed plants:
  • Gymnosperms: Open-seeded plants (e.g., conifers and cycads).
  • Angiosperms: Closed-seeded plants (flowering plants).
• Pteridophytes: Vascular plants that reproduce by means of spores. They produce neither flowers nor seeds and are sometimes referred to as "cryptogams" (e.g., ferns, horsetails, clubmoss).

Vascular Tissues in Pteridophytes

• Vascular bundles show variable arrangements of xylem and phloem at the central part of the stem.
• The central vascular cylinder found in roots, stems, and leaves is called the stele.

Types of Stele Found in Pteridophytes:

1. Protostele:

   The simplest and most primitive type of stele, consisting of a solid core of xylem surrounded by phloem. It lacks a central pith or any leaf gaps.

   • Subtypes: Haplostele, Actinostele.

   (Refer to page 18 for a diagram of Protostele.)

2. Siphonostele:

   A more advanced type of stele with a central pith surrounded by a ring of vascular tissue. It comprises leaf gaps.

   • Subtypes: Ectophloic Siphonostele, Soleno-stele, Dictyostele, Eustele.

   (Refer to page 19 for diagrams of different types of Siphonostele.)

   • Dictyostele: A type of siphonostele where the vascular cylinder is dissected by leaf gaps, forming a net-like appearance of vascular strands. Found in advanced ferns (e.g., Adiantum).
   • Eustele: Characterized by discrete vascular bundles arranged in a ring around the pith.

Vascular Tissues in Angiosperms

• In stems: Vascular tissue is organized into many discrete vascular bundles.
• In roots: Vascular tissue is organized within a single central vascular cylinder.
• Xylem: Presence of vessels.
• Phloem: Well-developed sieve tubes and companion cells.
• Four main types of vascular bundles: Collateral bundle, Bicollateral bundle, Concentric bundle, Radial bundle.

Vascular Tissues in Gymnosperms

• Xylem: Primarily consists of tracheids (elongated, dead cells with thick walls that conduct water); they have no vessels.
• Phloem: Contains sieve tubes (specialized cells that conduct sugars and other organic compounds); they have no companion cells.

Comparison of Pteridophytes, Gymnosperms, and Angiosperms