Modification of Leaves: Leaves can be modified in the form of spines that reduce water loss and also act as a defence. Some are modified into tendrils to provide support to the plant. Some leaves are thick that help in water storage. Some are modified to catch and digest insects.
Modification of Leaves
The xerophytic plants and plants belonging to the Crassulaceae family have thick and succulent leaves that store water in their tissues. The parenchymatous cells of these leaves have large vacuoles filled with hydrophilic colloid. This modification helps the plant to resist desiccation.
Leaf tendrils exist in plants with weak stems. The leaves get modified into thread-like structures called tendrils. These tendrils climb a nearby stick or wall and provide support to the plant. For eg., In Lathyrus aphaca, the whole leaf is modified into tendrils. The upper leaflets of Pisum sativum get modified into tendrils.
A few plants have their leaves modified into needle-like structures known as spines. The spines act as defensive structures. They also reduce water loss due to transpiration. For eg., in Opuntia, the leaves are modified into spines.
These are thin, membranous structures, without stalks, brownish or colourless in appearance. They protect the auxiliary bud present in their axil. Scale leaves in onion are fleshy and thick and store food and water. Casuarina and Asparagus also contain sale leaves
In some plants, the terminal leaflets of leaf get modified into hook-like structures that help them in climbing. Eg., Bignonia unguiscati.
In a few plants, one of the leaves present at the nodes gets modified into adventitious roots which helps them to float over the water surface. Eg., Salvinia
In some plants, the petiole becomes flattened, taking the shape of a leaf and turns green in colour. This is known as phyllode. For eg., Australian Acacia.
Few plants require nitrogen for their development. In such plants, the leaves are modified to catch and digest insects. Few of the modifications are mentioned below:
- Leaf Pitcher- In a few plants like Nepenthes, the leaf-lamina is modified into a pitcher-like structure. The insect is digested into the inner walls of the pitcher which secretes a digestive fluid into the pitcher cavity.
- Leaf Bladder- In such plants, the segments of the leaves are modified into bladders. These plants are found in water. The inner wall is provided with digestive glands which helps in digesting the trapped insect. For eg., Utricularia
- In Drosera– The lamina possesses numerous hair with a sticky globule at its tip containing digestive enzymes. The moment an insect sits on the lamina, the hair covers the insect completely.
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