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A Handbook of Biology

A bud is seen in the axil of petiole in simple and compound leaves, but not in

the axil of leaflets of the compound leaf. The compound leaves are 2 types.

Rachis

Palmately compound leaf: In this, leaflets are attached at a

common point (at the tip of petiole), e.g., silk cotton.

Pinnately compound leaf: In this, many leaflets are present on

a common axis, the rachis, which represents the midrib of the

leaf, e.g., neem.

3. PHÝLLØTÅXÝ

It is the pattern of arrangement of leaves on the stem or branch.

It is of 3 types:

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Alternate: A single leaf arises at each node in alternate manner. E.g.

China rose, Mustard & Sunflower.

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Opposite: A pair of leaves arise at each node and lie opposite to each

other. E.g. Calotropis And Guava

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Whorled: More than two leaves arise at a node and form a whorl. E.g.

Alstonia

(AIPMT 2013)

4. MØDÏFÏÇÅTÏØÑ ØF LËÅVËS

Leaves are modified to perform functions other

than photosynthesis.

In plants such as Australian acacia, the leaves

are small and short-lived. The petioles in these

plants expand, become green and synthesise

food.

Leaves of some insectivorous plants (e.g.

pitcher plant, Venus-fly trap) are also modified

leaves.

Leaves are modified into tendrils for climbing

(Pea Plant) and spines for defense (Cacti).

The fleshy leaves of onion and garlic store food.

THË ÏÑFLØRËSÇËÑÇË ÅÑD THË FLØWËR

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A flower is a modified shoot wherein the shoot apical meristem changes

to floral meristem.

Leaves

Modification of

leaf of Cactus for

protection

modified

into spines