Key Points
Key Points: The Root
- Root: Underground part of plant, develops from the radicle of embryo.
- Types of roots: Tap root (dicots), fibrous root (monocots), adventitious roots (from other plant parts).
- Functions: Absorption of water and minerals, anchorage, storage of food, synthesis of growth regulators.
- Root cap: Protects the tender root apex and helps in soil penetration.
- Regions of root: Meristematic (cell division), elongation (increase in length), maturation (differentiation and root hairs).
- Root hairs: Help in absorption of water and minerals from soil.
- Modifications: Support (prop, stilt), respiration (pneumatophores), storage (carrot, radish, turnip).
Key Points: The Stem
- Stem: Aerial part of the plant, develops from the plumule and bears nodes and internodes.
- Structure: Has nodes (leaf origin), internodes (between nodes) and buds (terminal and axillary).
- Functions: Supports the plant body and conducts water, minerals, and food.
- Food storage modification: Rhizome (ginger), tuber (potato), bulb (onion), corm (Colocasia).
- Support modification: Stem tendrils help in climbing (grapevine, cucumber).
- Protection & propagation: Thorns for protection (Citrus, Bougainvillaea); runners and stolons for vegetative propagation (strawberry, mint).
- Photosynthesis modification: Flattened stems (cladodes) perform photosynthesis (Opuntia).
Key Points: The Leaf
- Leaf: Lateral, green, flattened structure developing from the shoot apical meristem; the main organ for photosynthesis.
- Parts of a leaf: Leaf base, petiole, and lamina; an axillary bud is present in the axil.
- Types of leaves: Simple leaf (single blade, e.g., mango) and compound leaf (leaflets, e.g., neem, rose).
- Venation: Arrangement of veins; reticulate (dicots) and parallel (monocots).
- Phyllotaxy: Arrangement of leaves on the stem; alternate, opposite, and whorled.
- Functions: Photosynthesis, transport of water/food, and gas exchange.
- Modifications: Tendrils (climbing), spines (protection), pitcher (nutrition), hooks (support).
