Anatomy of Flowering Plants
NCERT Class 11 Biology • Chapter 6 Solutions
Anatomical Differences & Identification
1. Anatomical differences: (a) Monocot vs Dicot Root (b) Monocot vs Dicot Stem.
(a) Differences between Monocot and Dicot Root
| Feature | Dicot Root (e.g., Sunflower) | Monocot Root (e.g., Maize) |
|---|---|---|
| Pericycle | Gives rise to secondary roots and lateral meristem. | Gives rise to lateral roots only. |
| Vascular Bundles | Diarch to Hexarch (2-6 bundles). | Polyarch (More than 6 bundles). |
| Pith | Small or inconspicuous. | Large and well developed. |
| Cambium | Develops during secondary growth. | Absent. |
| Secondary Growth | Present. | Absent. |
(b) Differences between Monocot and Dicot Stem
| Feature | Dicot Stem | Monocot Stem |
|---|---|---|
| Hypodermis | Collenchymatous. | Sclerenchymatous. |
| Vascular Bundles | Arranged in a ring; Conjoint, open; Wedge shaped. | Scattered; Conjoint, closed; Oval shaped. |
| Bundle Sheath | Absent. | Sclerenchymatous bundle sheath present. |
| Phloem Parenchyma | Present. | Absent. |
| Pith | Present. | Absent. |
2. How would you ascertain whether a young stem is Monocot or Dicot?
To differentiate, observe the transverse section under a microscope for the following features:
- Arrangement of Vascular Bundles:
- If arranged in a ring around the pith $\rightarrow$ Dicot Stem.
- If scattered throughout the ground tissue $\rightarrow$ Monocot Stem.
- Type of Vascular Bundles:
- If Open (Cambium present) $\rightarrow$ Dicot Stem.
- If Closed (Cambium absent) and surrounded by bundle sheath $\rightarrow$ Monocot Stem.
- Pith: Presence of distinct pith confirms Dicot; absence indicates Monocot.
Anatomical Features & Stomata
3. Identification based on anatomical features.
Features Observed:
- Vascular bundles are conjoint, scattered, and surrounded by sclerenchymatous bundle sheath.
- Phloem parenchyma is absent.
Identification: These are characteristic features of a Monocot Stem.
4. What is stomatal apparatus? Explain with diagram.
Stomatal Apparatus: It is a structure present on the leaf epidermis responsible for gas exchange and transpiration. It consists of:
- Stomatal Aperture (Pore): The central opening through which exchange occurs.
- Guard Cells: Two specialized epidermal cells surrounding the pore. They regulate opening and closing.
- Dicots: Bean-shaped.
- Monocots: Dumb-bell shaped.
- Subsidiary Cells: Specialized epidermal cells surrounding the guard cells that provide support.
Tissues & Leaf Structure
5. Name the three basic tissue systems in flowering plants.
| Tissue System | Tissues Included |
|---|---|
| 1. Epidermal Tissue System | Epidermis, Stomata, Epidermal appendages (Trichomes, Root hairs). |
| 2. Ground (Fundamental) Tissue System | Parenchyma, Collenchyma, Sclerenchyma (forming Cortex, Pericycle, Pith, Medullary rays). Mesophyll in leaves. |
| 3. Vascular Tissue System | Xylem and Phloem (Complex tissues). |
6. How is the study of plant anatomy useful to us?
- Solving Taxonomic Problems: Anatomy helps in establishing relationships between different plant groups and classifying them correctly.
- Understanding Physiology: It helps us understand how plants function (e.g., transport of water via xylem, food via phloem).
- Timber Identification: Helps in identifying quality wood and detecting adulteration in timber and spices.
- Pharmacognosy: Helps in identifying medicinal plants and checking the purity of herbal drugs.
- Crop Improvement: Understanding anatomy helps in breeding plants with better mechanical strength or resistance.
7. Describe the internal structure of a dorsiventral leaf.
A Dorsiventral (Dicot) Leaf shows the following distinct regions:
- Epidermis: Upper (adaxial) and Lower (abaxial) epidermis covered by cuticle. Stomata are more numerous on the lower epidermis.
- Mesophyll: Differentiated into two types of parenchyma:
- Palisade Parenchyma: Elongated cells arranged vertically below the upper epidermis; rich in chloroplasts.
- Spongy Parenchyma: Oval/round cells loosely arranged below palisade cells; contain air cavities for gas exchange.
- Vascular System: Vascular bundles are conjoint and closed. They are surrounded by a layer of thick-walled bundle sheath cells. The size of bundles varies with the size of veins (reticulate venation).