Modification of Leaves-Leaf tendrils, Leaf spines, Leaf scale, Phyllode, Pitcher, Bladder

The leaf can be defined as a lateral outgrowth of the stem arising from the node and having a bud in its axil. Leaves are flat, green in color due to the presence of chlorophyll. Leaf helps to manufacture food for the whole plant body. Besides their normal function of photosynthesis, gaseous exchange and transpiration,
leaves or their parts may get modified to perform special functions such as protection, food storage, climbing, etc. Some important modifications of leaves are as leaf tendrils, leaf spines, leaf scale, phyllode, pitcher and bladder.

Leaf-tendrils: The leaf may be wholly or partially modified to form a thin wiry closely coiled structure called tendrils. These are climbing organs and sensitive to contact with a foreign body. In some climbers, the terminal leaflet is modified into sharp, stiff, curved hooks which act as organs of support, e.g. pea, bignonia, smilax, wild pea, etc.

Leaf Spines: In certain plants, the leaf is replaced by a hard, pointed structure called spine for the purpose of defense. Spines may develop at the leaf apex or on the margin or both, e.g. date palm, aloe, prickly pear, barberry, etc.

Leaf Scales: These are thin, dry, membranous, non-green structures generally protective in function but may become thick and fleshy with food and water retention, e.g. casuarinas, ficus and underground stems like corm, ginger, etc.

Phyllode: Unlike phylloclade in which the stem becomes flat, green and photosynthetic, in a phyllode, it is the petiole that becomes expanded and photosynthetic. The function of the leaf is to taken over by the petiole since the leaf itself is reduced or completely shed in order to cut down water loss by transpiration, e.g. Australian acacia, Parkinsonia aculeate.

Pitcher: In the pitcher plant, (Nepenthes), the leaf blade is modified into a pitcher like structure with a lid which covers the mouth of the pitcher. The function of this modification is to help the plant to trap and digest insects, e.g. nepenthes.

Bladder: In Utricularia, floating water weed, some of the segments of the leaves develop bladder like structures with a trap-door entrance; this helps to trap tiny aquatic organisms, e.g. Utricularia (Blasser wort).