Plant Anatomy: Root Structures

Study Notes

External Structures

Roots are cylindrical and branching structures that grow underground (generally, if: below ground: root system, above ground: shoot system)
The first root to emerge from a seed is called a radical, which develops into the primary root
Root types: Diffuse or fibrous, Taproot or primary, Adventitious

Internal Structures

The root tip contains several distinct regions:
- Root cap: Protects the root apical meristem
- Quiescent center: Region of inactive cells that function as a cellular reserve
- Region of cell division (meristematic region): New cells are formed via mitosis
- Region of cell elongation: Cells increase in length
- Region of cell differentiation: The youngest part of this region is the root hair zone
Root internal structure:
- Epidermis: Absorbs water and dissolved materials from the soil
- Cortex: Largest cross-section of the root, contains parenchyma cells (for food storage), hypodermis (outermost layer), and endodermis (innermost layer)
- Endodermis: Controls the movement of water and dissolved materials into the xylem
- Vascular cylinder (stele): Consist of xylem (carries water) and phloem (carries food)

Root Types and modifications

Diffuse or fibrous roots: Many thin, hair-like root branches, better at holding soil, less tolerant to drought, found in monocots
Taproot or primary root: Main root with minimal branching, found in dicots
Adventitious roots: Grow above ground from the stem or leaves, perform the same function as roots
Specialized roots:
- Prop/stilt roots: Above ground roots that help with stability (common in monocots, e.g., corn)
- Fleshy roots: Enlarged taproots for food storage, often used for consumption
- Fascicled roots: Fibrous roots with swollen parts for food storage
- Aerial roots: Grow above ground to absorb moisture and nutrients
- Buttress roots: Large, wide roots that provide stability to shallowly rooted trees
- Pneumatophore: Aerial roots that grow above the water surface to facilitate aeration
- Contractile roots: Adventitious roots that pull the plant down into the soil
- Photosynthetic roots: Green roots that perform photosynthesis
- Parasitic roots: Roots that penetrate into the host plant's conducting tissues to extract nutrients
- Mycorrhizal roots: Symbiotic association with soil fungus to help the plant absorb minerals

Functions of Roots

Anchorage: Roots anchor the plant in the soil
Absorption: Roots absorb water and dissolved nutrients from the soil
Conduction: Roots transport water and nutrients to the rest of the plant
Food storage: Roots store food reserves

Description

Explore the fascinating world of plant root structures in this quiz. Test your knowledge on the external and internal structures of roots, including root types and their functions. Understand how roots contribute to plant growth and survival.