Key Points
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: Structure of a Dicotyledonous Seed
- Seed coat: Consists of two layers—testa (outer) and tegmen (inner).
- Hilum: A scar on the seed coat showing the point of attachment to the fruit.
- Micropyle: A small pore present above the hilum helps in water absorption.
- Cotyledons: Two fleshy cotyledons present, storing reserve food material.
- Embryo: Contains an embryonal axis with radicle and plumule at opposite ends.
- Endosperm: May be present (e.g., castor) or absent (e.g., bean, gram, pea) in mature seeds.
Concepts [16]
- Morphology and Modifications of Root, Stem, Leaf
- Types of Root
- Modifications of Roots for Storage, Respiration (Pneumatophores) and Support (Stilt and Prop)
- Stems
- The Stem
- Leaves
- Types of Leaves
- Phyllotaxy – Alternate, Opposite, Whorled (With an Example of Each)
- Modifications for Mechanical Support, Protection, Storage, Reproduction; Insectivorous Plant (Pitcher Plant, Venus-fly-trap
- Morphology of Flower, Fruit and Seed
- Types of Inflorescence (Racemose and Cymose)
- Structure of a Typical Flower
- Fruits to Be Classified into True and False, Structure of a Typical Fruit (Mango and Coconut)
- Structure of a Dicotyledonous Seed
- Non-Albuminous and Albuminous, Perisperm
- Description of Families – Solanaceae, Fabaceae and Liliaceae
