Glycosphingolipids as determinants of blood groups.

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 Glycosphingolipids as determinants of blood groups.

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III. Underground Stem modification

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Feature of leaves

A typical leaf consists of three main parts;

a) Leaf base

b) Petiole

c) Lamina

Feature of leaves

leaf base and may bear two lateral small leaf like structures called stipules.

In some leguminous plants the leaf base may become swollen, which is called the Pulvinus

Feature of leaves

The lamina or the leaf blade is the green expanded part of the leaf with veins and veinlets. There is, usually, a middle prominent vein, which is known as the midrib.

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Venation

The arrangement of veins and the veinlets in the lamina of leaf is termed as venation

Venation

When the veinlets form a network, the venation is termed as reticulate that possesses in dicotyledonous plants

When the veins run parallel to each other within a lamina, the venation is termed as parallel is the characteristic of most monocotyledons.

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Types of Leaf

Simple Leaf

Compound Leaf

The compound leaves may be of two types;

A number of leaflets are present on a common axis, the rachis, which represents the midrib of the leaf called Pinnately compound leaf

Ex- Neem 

The leaflets are attached at a common point, such as at the tip of petiole, called Palmately compound leaf

EX- poison ivy, familiar house plant Schefflera sp. (commonly called “umbrella plant”)

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Phyllotaxy

This is usually are of four types – alternate, opposite, spiral and whorled

In alternate type of phyllotaxy, a single leaf arises at each node in alternate manner, as in china rose, mustard and sunflower plants

Phyllotaxy

In opposite type, a pair of leaves arise at each node and lie opposite to each other as in Calotropis and guava plants.

If more than two leaves arise at a node and form a whorl, it is called whorled, as in Alstonia (Devil Tree) Apocynaceae

Spiral phyllotaxy

Fibonacci sequence

Golden Angle

the divergence angle between successively arising leaves is fixed at the golden angle of 137.5°