CBSE Class 11-science Answered
Modification of stem:
1. Underground stem: Stores food. It also acts as organs of perennation to face conditions unfavourable for growth. Examples: Potato, turmeric
2. Stem tendrils: They develop from axillary buds. They are slender, spirally coiled and help plants to grow. Example: Pumpkins
3. Thorns: Axillary buds get modified into thorns. They are woody, straight and pointed.
They protect plants from animals. Example: Citrus
4. Photosynthetic stem: In arid regions, stems become flat and fleshy. They contain chlorophyll to carry out photosynthesis. Example: Euphorbia
5. Reproductive stems:
In some plants such as Jasmine, a slender lateral branch arises from the base of the main axis. After growing aerially for some time, it arches down to touch the ground.
In plants such as Chrysanthemum, the lateral branches originate from the basal and underground portion of the main stem. It grows horizontally beneath the soil and comes out obliquely upwards to give rise to leafy shoots.