Describe the aerial modifications of the stem.
The aerial modifications of the stem are: - a) Stem Tendril: - Stem tendrils are thin, leafless, slender-like and spirally coiled structures that develop from axillary buds. They help the plants such as cucumber, watermelon, grapevine etc. to climb. b) Stem Thorn: - sometimes the axillary buds grow into hard, woody straight & pointed structures called thorns. It arises in the axil of the leaf or at the tip of the branch. Sometimes thorn bears leave also. Example: - Citrus, Bougainvillea etc. c) Phylloclade: - It is the green flattened or cylindrical stem that takes the form and function of the leaf. They contain chlorophyll & carry photosynthesis. They have many nodes & internodes. Their actual leaves are scales or shortened spines. It is commonly found in xerophytic plants. Example: - Opuntia, epiphyllum etc. d) Cladode: - This is a phylloclade of limited growth which develops, from the node of the stem or branch and in the axil of a scale leaf. Cladodes are green flat and leaf-like structures that carry on photosynthesis. Example: - Asparagus, Ruscus, etc. e) Bulbils: - This is a modified vegetative or floral bud meant for the production of a new plant. It detaches itself from its mother plant and grows into an independent plant. Example: - Oxalis, Agave americana, Lilium.
