Notes on Anatomy of Flowering Plants

Overview of structural similarities and differences between organisms, including plants and animals.
Focus of the chapter:
- Internal structure and functional organization of higher plants.
- Study of internal structure known as anatomy.
- Plants consist of:
- Cells: Basic unit of life.
- Tissues: Cells organized into functional groups.
- Organs: Tissues grouped to form organs.
Differences in internal structures reflected in:
- Various plant organs.
- Anatomical distinctions between monocots and dicots.
- Adaptations to different environmental conditions.

Types of plant tissues vary based on location and structure.
Primary classification of tissue systems:
- Epidermal Tissue System
- Ground or Fundamental Tissue System
- Vascular or Conducting Tissue System

Description and composition:
- Outermost covering of the plant body.
- Comprises:
- Epidermal cells: Generally compact and elongated.
- Stomata: Structures that facilitate gas exchange and transpiration.
- Epidermal appendages: Includes trichomes and hairs.
Roles and functions:
- Root hairs: Unicellular extensions aiding in water and mineral absorption.
- Trichomes:
- Usually multicellular, can be branched or unbranched.
- Functions include reducing water loss through transpiration.
Structure of stomata:
- Guard cells:
- Bean-shaped cells that regulate stomatal pore.
- In grasses, they may have a dumb-bell shape.
- Possess chloroplasts and vary in cell wall thickness (thin outer, thick inner).
- Stomatal Apparatus:
- Composed of:
  - Stomatal pore
  - Guard cells
  - Subsidary cells

Comprises all tissues except epidermis and vascular bundles.
Types of simple tissues in ground tissue:
- Parenchyma: Found in cortex, pericycle, pith, and medullary rays; involved in storage and photosynthesis (in leaves = mesophyll).
- Collenchyma: Provides mechanical support.
- Sclerenchyma: Provides rigidity.
Main components of ground tissue:
- Cortex: Comprised mostly of parenchyma, with intercellular spaces.
- Endodermis: Innermost layer of the cortex; barrel-shaped cells with casparian strips (water-impermeable) on the radial and tangential walls.
- Pericycle: Layer of cells next to endodermis; origins of lateral roots and vascular cambium.
- Pith: Central region, often small and inconspicuous.

Composed of complex tissues: Phloem and Xylem.
Structure of vascular bundles:
- In dicots, cambium present between phloem and xylem (called open vascular bundles) allowing secondary growth.
- In monocots, vascular bundles lack cambium (called closed vascular bundles) and do not support secondary growth.
Arrangements of vascular bundles:
- Radial Arrangement: Found primarily in roots; separate xylem and phloem.
- Conjoint Arrangement: Xylem and phloem situated along the same radius, typical in stems and leaves; phloem positioned outside xylem.

Study of transverse sections of roots, stems, and leaves provides insights into tissue organization.

Examination of transverse section reveals:
- Epiblema: Outermost layer with root hairs for absorption.
- Cortex: Layers of parenchyma cells with air spaces; the innermost layer is the endodermis with casparian strips.
- Pericycle: Thick-walled parenchymatous cells; origin of lateral roots.
- Steles: Vascular bundles housed within the pericycle.
Typical characteristics:
- Usually two to four patches of xylem and phloem.
- Cambium may develop in secondary growth.

Anatomical similarities to dicot roots but distinct features:
- Generally more than six xylem bundles (polyarch).
- Well-developed pith.
- Does not undergo secondary growth.

Each section features:
- Epidermis: Outermost layer with cuticle; may have trichomes and stomata.
- Cortex: Contains hypodermis (collenchyma), parenchyma, and endodermis (starch sheath).
- Pericycle and vascular bundles: Arranged in a ring with cambium present between xylem and phloem.
- Pith: Central parenchymatous cells with intercellular spaces.

Structure includes:
- Sclerenchymatous hypodermis.
- Scattered vascular bundles each with a sclerenchymatous sheath.
- Large parenchymatous ground tissue between vascular bundles.

Layered configuration:
- Epidermis: Upper (adaxial, thicker cuticle) and lower (abaxial, often more stomata).
- Mesophyll: Two types of parenchyma (palisade and spongy) responsible for photosynthesis.
- Vascular System: Vascular bundles in veins and midrib; bundles encased in bundle sheath cells.

Structure features:
- Stomata on both surfaces; mesophyll not differentiated (no palisade or spongy types).
- Presence of bulliform cells: Turgidity enables the leaf to flatten; flaccidity causes curling to minimize water loss.
- Parallel venation evident in vascular bundle size uniformity (except in major veins).

Plant anatomy consists of diverse tissue types classified into:
- Meristematic Tissues: Apical, lateral, intercalary.
- Permanent Tissues: Simple and complex.
Functions of plant tissues:
- Food assimilation/storage, water/mineral transportation, mechanical support.
The three tissue systems and their components:
- Epidermal: Epidermal cells, stomata, appendages.
- Ground: Cortex, pericycle, pith.
- Vascular: Xylem and phloem, type influenced by cambium.
Anatomical variances in monocots and dicots essential for understanding plant biology and their adaptation strategies.

Illustrate anatomical differences between monocot and dicot roots, stems.
Cut and observe a transverse section of a young stem; differentiate monocot from dicot.
Identify plant material with:
- Characteristics: Conjoint, scattered vascular bundles; absent phloem parenchyma.
Explain stomatal apparatus structure with a diagram.
Name and categorize the three basic tissue systems.
Evaluate the usefulness of studying plant anatomy.
Describe dorsiventral leaf structure with diagrams.