Summary & Tables: Anatomy of Flowering Plants
The Three Tissue Systems
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| System | Components | Function & Characteristics |
|---|---|---|
| Epidermal Tissue System | Epidermal cells, Stomata, Trichomes (stem hairs), Root hairs. |
Epidermis: Outermost layer, usually single-layered, parenchymatous with cuticle (absent in roots). Stomata: Regulate transpiration. Bean-shaped guard cells (dicots) or dumb-bell shaped (grasses). Hairs: Root hairs absorb water; Trichomes prevent water loss. |
| Ground Tissue System | Parenchyma, Collenchyma, Sclerenchyma (Cortex, Pericycle, Pith, Medullary rays). |
Forms the bulk of the plant tissues between epidermis and vascular bundles. In leaves, it forms the Mesophyll (chloroplast-containing). |
| Vascular Tissue System | Xylem, Phloem (Complex Tissues). |
Radial: Xylem and phloem on different radii (Roots). Conjoint: Xylem and phloem on same radius (Stems/Leaves). Open: Cambium present (Dicot stems). Closed: Cambium absent (Monocots). |
Anatomy of Root: Dicot vs. Monocot
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| Feature | Dicot Root (e.g., Sunflower) | Monocot Root |
|---|---|---|
| Cortex | Several layers of thin-walled parenchyma. | Similar to dicot. |
| Endodermis | Single layer with water-impermeable waxy Casparian strips. | Present with Casparian strips. |
| Pericycle | Thick-walled parenchyma. Initiates lateral roots and vascular cambium. | Present. |
| Vascular Bundles | Usually 2 to 4 patches (Diarch to Tetrarch). | Usually more than six (Polyarch). |
| Pith | Small or inconspicuous. | Large and well-developed. |
| Secondary Growth | Occurs (Cambium ring develops). | Does not undergo secondary growth. |
Anatomy of Stem: Dicot vs. Monocot
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| Feature | Dicot Stem | Monocot Stem |
|---|---|---|
| Hypodermis | Collenchymatous (mechanical strength). | Sclerenchymatous. |
| Ground Tissue | Differentiated into Cortex, Pericycle, and Pith. | Undifferentiated large parenchymatous mass. |
| Vascular Bundles | Arranged in a Ring. Conjoint, Open, with Endarch protoxylem. | Scattered. Conjoint, Closed. Peripheral bundles smaller than central ones. |
| Bundle Sheath | Absent. | Sclerenchymatous bundle sheath surrounds VBs. |
| Phloem Parenchyma | Present. | Absent. |
| Water Cavities | Absent. | Present within vascular bundles. |
Anatomy of Leaf: Dorsiventral vs. Isobilateral
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| Feature | Dorsiventral (Dicot) Leaf | Isobilateral (Monocot) Leaf |
|---|---|---|
| Stomata | More on abaxial (lower) epidermis. | Present on both surfaces of the epidermis. |
| Mesophyll | Differentiated into Palisade and Spongy parenchyma. | Not differentiated into palisade and spongy parenchyma. |
| Special Cells | Absent. | Bulliform cells (large, colorless, empty cells) in adaxial epidermis (grasses). |
| Venation Pattern | Reticulate (Vascular bundles vary in size). | Parallel (Vascular bundles nearly similar in size, except main veins). |
Chapter Summary
Anatomy is the study of the internal structure of plants. Tissues are organised into three systems based on location: Epidermal, Ground, and Vascular.
Key Definitions & Structures:
- Stomatal Apparatus: Consists of the stomatal aperture, guard cells, and subsidiary cells. Guard cells are dumb-bell shaped in grasses (monocots) and bean-shaped in dicots.
- Casparian Strips: Water-impermeable waxy material (suberin) found in the endodermis of roots.
- Stele: All tissues on the inner side of the endodermis, including pericycle, vascular bundles, and pith.
- Bulliform Cells: Large, empty cells in grasses that become turgid to expose leaves or flaccid to curl leaves inwards to minimize water loss.
- Endarch vs. Exarch: In stems, protoxylem is towards the center (Endarch). In roots, protoxylem is towards the periphery (Exarch).
Structural Adaptations: The internal structure shows adaptations to diverse environments. For example, the cuticle prevents water loss, and trichomes help in reducing transpiration. The presence of cambium in dicots allows for secondary growth (increase in girth), which is absent in monocots.