Introduction
Anatomy of flowering plants deals with the internal structure of plant organs such as roots, stems, and leaves. It helps us understand how different tissues are organized and how they perform specific functions.
Plant anatomy mainly focuses on tissues, tissue systems, and secondary growth, which are essential for plant growth and survival.
Plant Tissues
A tissue is a group of cells that have a common origin and perform a specific function.
Plant tissues are broadly classified into:
- Meristematic tissues
- Permanent tissues
Meristematic Tissues
Meristematic tissues consist of actively dividing cells and are responsible for plant growth.
Characteristics of Meristematic Tissue
- Cells are small and have dense cytoplasm
- Nucleus is prominent
- Vacuoles are absent or very small
- Cells divide continuously
Types of Meristematic Tissues
1. Apical Meristem
Apical meristems are present at the tips of roots and shoots. They are responsible for the increase in length of the plant.
2. Intercalary Meristem
Intercalary meristems are located at the base of leaves or internodes. They help in the elongation of internodes, especially in grasses.
3. Lateral Meristem
Lateral meristems, such as vascular cambium and cork cambium, are responsible for the increase in girth of the plant.
Permanent Tissues
Permanent tissues are formed from meristematic tissues after cell differentiation. These cells lose their ability to divide.
Types of Permanent Tissues
1. Simple Permanent Tissues
These tissues are made up of similar types of cells.
Parenchyma
Parenchyma cells are living cells with thin cell walls. They perform functions such as storage, photosynthesis, and secretion.
Collenchyma
Collenchyma cells provide mechanical support and flexibility. Their walls are unevenly thickened.
Sclerenchyma
Sclerenchyma cells are dead cells with thick, lignified walls. They provide strength and rigidity to the plant.
2. Complex Permanent Tissues
These tissues consist of different types of cells working together.
Xylem
Xylem is responsible for the transport of water and minerals from roots to other parts of the plant.
Components of xylem:
- Tracheids
- Vessels
- Xylem fibres
- Xylem parenchyma
Phloem
Phloem transports food (organic substances) throughout the plant.
Components of phloem:
- Sieve tubes
- Companion cells
- Phloem fibres
- Phloem parenchyma
Tissue Systems
Plant tissues are organized into three major tissue systems:
1. Epidermal Tissue System
The epidermis is the outermost layer of the plant body. It protects the plant from injury and water loss.
Components:
- Epidermis
- Stomata
- Trichomes
2. Ground Tissue System
The ground tissue system forms the bulk of the plant body and includes parenchyma, collenchyma, and sclerenchyma.
It is responsible for storage, photosynthesis, and support.
3. Vascular Tissue System
This system includes xylem and phloem and is responsible for the conduction of water, minerals, and food.
Anatomy of Dicot and Monocot Roots
Dicot Root
- Vascular bundles are radial
- Xylem is usually tetrarch (four arms)
- Pith is small or absent
Monocot Root
- Vascular bundles are numerous
- Pith is large
- Xylem is polyarch
Anatomy of Dicot and Monocot Stems
Dicot Stem
- Vascular bundles arranged in a ring
- Open vascular bundles (cambium present)
- Secondary growth present
Monocot Stem
- Vascular bundles scattered
- Closed vascular bundles (no cambium)
- No secondary growth
Anatomy of Leaf
Dorsiventral Leaf (Dicot Leaf)
- Upper and lower surfaces are different
- Mesophyll differentiated into palisade and spongy tissues
Isobilateral Leaf (Monocot Leaf)
- Both surfaces are similar
- Mesophyll not differentiated
Secondary Growth
Secondary growth refers to the increase in girth (thickness) of stems and roots.
Vascular Cambium
- Produces secondary xylem (inside)
- Produces secondary phloem (outside)
Cork Cambium (Phellogen)
- Produces cork (outer layer)
- Forms protective covering
Annual Rings
- Formed due to seasonal variations
- Used to determine age of tree
Important Differences
Dicot vs Monocot Stem
| Feature | Dicot Stem | Monocot Stem |
|---|---|---|
| Vascular bundles | Ring | Scattered |
| Cambium | Present | Absent |
| Secondary growth | Present | Absent |
Xylem vs Phloem
| Feature | Xylem | Phloem |
|---|---|---|
| Function | Water transport | Food transport |
| Cells | Mostly dead | Mostly living |
Important NEET & CBSE Points
- Meristematic tissues are actively dividing
- Xylem transports water, phloem transports food
- Cambium causes secondary growth
- Dicot stem shows secondary growth
- Monocots generally lack secondary growth
Quick Revision Notes
- Meristem → growth
- Parenchyma → storage
- Xylem → water
- Phloem → food
- Cambium → thickness
Frequently Asked Questions (FAQs)
Q1. What is plant anatomy?
Study of internal structure of plants.
Q2. What is cambium?
Meristem responsible for secondary growth.
Q3. What is the function of xylem?
Transport of water and minerals.
Q4. What is secondary growth?
Increase in girth of plant.
Conclusion
Anatomy of flowering plants helps in understanding the internal organization and functioning of plant tissues. It is a highly important chapter for CBSE exams and NEET, especially for diagram-based questions and conceptual clarity.