Type and functions of leaf

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Understand about the leaf

A leaf is a lateral dissimilar appendage of the stem borne at a node and subtending a bud in its axil. It is a partial stem or branch having a limited growth. It is normally green, flattened structure and is regarded as the most important vegetative part of the plant since food material is prepared in it. Leaves develop from the swollen exogenous protuberances on the growing apex called the leaf primordia. They always follow an acropetal order of development.

TYPES OF LEAVES

According to the origin and function of leaves, they can be grouped into following types: 

Cotyledonary leaves or seed leaves:  These are embryonic leaves of seeds which may be fleshy due to accumulation of food e.g., beans, grams, etc. or thin, flat with vein marking, e.g., castor (Ricinus communis).

Cataphylls or scale leaves: These are small, sessile, non-green, dry and papery or fleshy. They may also be found on aerial parts as on bamboo, Casuarina, Asparagus, etc. A bud is present in the axil of each scale leaf. They protect the young bud but in some plants like onion and garlic, these also store food.

Hypsophylls or bract leaves:  These are special  leaves which contain  flower or inflorescence in their axils. These are usually small and green but in Bougainvillea and Euphorbia, these are large and brightly coloured to attract insects. They protect flower buds.

Prophylls: First few leaves on a stem, different from other leaves are termed prophylls. Usually there is one prophyll in monocots and two in dicots. In wood apple (Aegle marmelos) prophylls are represented by spines.

Floral leaves and sporophylls: These are specialized and modified leaves present in flower. They are sepals, petals, tepals, stamens and carpels. Of these, the stamens and carpels may also be termed as sporophylls. Sepals are green and protective while petals are coloured and attractive. The stamens and carpels take part in sexual reproduction.

Foliage leaves: They are the common green leaves attached on aerial stem and branches. They perform the function of photosynthesis.

Refer NCERT Solutions for class 12 Biology for exercise given in NCERT text book also go for online test for class 11 botany to find your error .

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