Morphology & Anatomy
[PREMIUM NCERT MODULE • STRUCTURAL ORGANIZATION]
- Root: Tap root (Dicots); Fibrous (Monocots).
--> Modifications: Prop (Banyan), Stilt (Maize), Pneumatophores (Rhizophora). - Stem: Nodes and Internodes.
--> Modifications: Tendrils (Gourds), Thorns (Citrus), Phylloclade (Opuntia - photosynthetic stem). - Leaf: Reticulate (Dicots) vs Parallel (Monocots) venation.
--> Phyllotaxy: Alternate (Sunflower), Opposite (Calotropis), Whorled (Alstonia).
A. Tissues:
- Meristematic: Apical (height), Intercalary (grasses), Lateral (vascular cambium/cork cambium for girth).
- Permanent: Parenchyma (storage), Collenchyma (mechanical support - living), Sclerenchyma (dead - fibers/sclereids).
B. Vascular Bundles:
- Radial: Xylem/Phloem on different radii (Roots).
- Conjoint: Together on same radius (Stems/Leaves).
--> Open: Cambium present (Dicot stems).
--> Closed: No cambium (Monocot stems).
| Feature | Dicot Stem | Monocot Stem |
|---|---|---|
| Vascular Bundles | Arranged in ring | Scattered |
| Bundle Sheath | Absent | Present (Sclerenchymatous) |
| Secondary Growth | Present | Absent |
| Feature | Dicot Root | Monocot Root |
|---|---|---|
| Xylem bundles | 2 to 4 (Diarch-Tetrarch) | More than 6 (Polyarch) |
| Pith | Small/Inconspicuous | Large and well-developed |
Increase in girth due to Lateral Meristems (Vascular & Cork cambium).
- Spring wood: Light colored, wide vessels (Early wood).
- Autumn wood: Dark colored, narrow vessels (Late wood).
- Heartwood: Central, dark, durable (dead elements).
- Sapwood: Peripheral, light, conducts water.
Morphology & Anatomy HOTS Questions
[ ADAPTATION & TISSUE SYSTEMS ]
Rhizophora grows in swampy, waterlogged areas where oxygen is not available to the roots. Pneumatophores are negatively geotropic (grow upward) roots that possess small pores called lenticels/pneumathodes for gas exchange (intake of oxygen for respiration).
The Casparian strip is a deposition of water-impermeable, waxy material (Suberin) on the radial and tangential walls of Endodermal cells. It forces water and solutes to cross the endodermis through the protoplast (Symplastic pathway), allowing the plant to regulate what enters the vascular cylinder.
Endarch: Protoxylem lies toward the center (Pith) and Metaxylem toward the periphery. Seen in
Stems.
Exarch: Protoxylem lies toward the periphery and Metaxylem toward the center.
Seen in Roots.
Annual rings (Spring + Autumn wood) are formed due to seasonal variations in the activity of vascular cambium. In tropical coastal regions (like Mumbai or Kerala), the climate is uniform throughout the year. Therefore, the cambium remains equally active, and no distinct seasonal bands are formed.
Heartwood (Duramen): Central, dark, non-functional (blocked by Tyloses and tannins),
resistant to pathogens, provides only mechanical strength.
Sapwood (Alburnum): Peripheral,
light, functional (conducts water and minerals).
Vexillary (Papilionaceous); consists of Standard, Wings, and Keel.
Parietal; ovules develop on the inner wall of the ovary.
Ebracteate, actinomorphic, bisex, K(5) C(5) A5 G(2) superior.
Cellulose, hemicellulose, and pectin at the corners.
Stomatal aperture, Guard cells, and Subsidiary cells.
Monocot stems (vascular bundles are scattered).
In Grasses; help in rolling/unrolling leaves to minimize water loss.
Phellem (cork), Phellogen (cork cambium), and Phelloderm (secondary cortex).
Pteridophytes and Gymnosperms (they have albuminous cells).
Stomata only on the lower surface (Dicot leaves).
China rose (Malvaceae family pattern).
The shield-shaped single cotyledon.
Absent (except Dracaena/Yucca).
Provide gritty texture to guava, pear, and sapota.
Dead, long, cylindrical tubelike structures with lignified walls.
Morphology & Anatomy: 50 Mastery Facts
Premium Rapid Revision