Structural Variation in Angiospermic leaf

Subject: Biology

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Overview

Leaf is a lateral dissimilar appendage of a plant body which arises on the node of stem and bears axillary bud on its axil. This note contains detail information about shape, apex, surface, margin, texture, phyllotaxy of leaf.
Structural Variation in Angiospermic leaf

Shape of leaf

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Acicular: Elongated pointed needle-shaped leaf. Eg; Pinus

Linear: Elongated, narrow flattened leaf. Eg; Grasses, Zea Hays.

Lanceolate: Elongated sword-like leaf. Eg; Nerium

Elliptic: Ellipse shaped leaf. Eg; Psidium Gwasava (Gawa)

Cordate: Hard shaped leaf or leaf with a notched base and pointed apex. Eg; Piper betel.

Obcordate: Leaf with notched apex and rounded or pointed base. Eg; Bauhinia

Ovate: Egg-shaped leaf or leaf with the broad base and narrow apex. Eg; Hibiscus

Obovate: Leaf with broad apex and narrow or pointed base. Eg; Terminalia

Oblong: Elongated rectangular leaf. Eg; Musa( Banana)

Hastate: Arrowhead-shaped leaf. Eg; upper leaf of Brassica Campestris.

Lyrate: Lyre-shaped leaf or leaf with large terminal lobe and small lateral lobes. Eg; Brassica Campestris

Apex of leaf

Acute: Leaf with a pointed apex.

Obtuse: Leaf with rounded apex.

Accuminate: Leaf with pointed apex in which extreme apex is drawn out into an elongated tale like structure.

Mucronate: Leaf with rounded or pointed apex in which short pointed outgrowth appears at the extreme tip.

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Surface of Leaf

Glabrous: Leaf with a smooth or non-hairy surface.

Glaucous: Leaf with the smooth and shiny surface. Eg: Rubber plant.

Pubescent: Leaf with the hairy surface. Eg: Geranium

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Margin of Leaf

Entire: Leaf with the smooth margin.

Repand: Leaf with slightly or lightly wavy margin.

Sinuate: Leaf with deeply wavy margin.

Serrate: Leaf with a saw - like margin in which teeth are directed towards the apex.

Serrulate: Leaf with finely serrated margin.

Dentate: Leaf with toothed margin in which teeth are outwardly directed.

Runcinate: Leaf with a saw- like margin in which teeth are directed towards the leaf base.

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Texture of leaf

Herbaceous: Thin and soft textured leaf. Eg; Rose

Coriaceous: Thick firm and leathery texture. Eg; Rubber plant

Succulent: Thick and fleshy leaf which stores water in the form of mucilage. Eg; Aloe vera

Duration of leaf

Caducous: Leaves falling off much earlier in the life.

Deciduous: Leaves remaining intact at least for one season.

Persistent: Leaves remaining intact for whole life.

Insertion of Leaf

Cauline: Leaves arising on the main stem. Eg; Maize

Ramal: Leaves arising on the branches. Eg; All trees

Radical: Leaves arising in a cluster or in a rosette form from the reduced stem known as disc than it is known as radical leaves. Eg; Radish, Turnip.

Phyllotaxy

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The mode of arrangement of leaves on the node of the stem is known as phyllotaxy. It is of three types;

Alternate/Spiral

If single leaf arises on a node and leaves of adjacent nodes lie alternately to each other then it is known as alternate phyllotaxy. Eg; Tulsi

Opposite

If a pair of leaves arise on a node and lie opposite to each other than it is known as opposite phyllotaxy. If a pair of leaves on adjacent nodes occur on the same plane than it is known as superposed opposite phyllotaxy. If a pair of leaves on adjacent node lie perpendicular to each other than it is known as decussate opposite phyllotaxy.

Whorled:

If a cluster of leaves arises on a node then it is known as whorled phyllotaxy.

Things to remember
  • Leaf is a lateral dissimilar appendage of a plant body which arises in the node of stem and bears axillary bud in its axil. 
  •  Leaves arising in a cluster or in a rosette form from the reduced stem known as disc than it is known as radical leaves. Eg; Radish, Turnip.
  • The mode of arrangement of leaves on the node of the stem is known as phyllotaxy. 
  • If single leaf arises on a node and leaves of adjacent nodes lie alternate to each other then it is known as alternate phyllotaxy. Eg; Tulsi
  • If a cluster of leaves arises on a node then it is known as whorled phyllotaxy.

 

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  • There can be more than one community in a society. Community smaller than society.
  • It is a network of social relationships which cannot see or touched.
  • common interests and common objectives are not necessary for society.

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