Describe modifications of the stem with suitable examples

Explanation-

The stem may be aerial, sub-aerial, or underground.

Modifications of Aerial Stems-
Stem tendrils- They are thread-like structures that are coiled around support and help the plant in climbing. For Example- Grapevine, Cucurbita.

Stem thorns-They is the sharp, stiff structure that has lost its power of growing and becomes hard. For example- Duranta, Bougainvillea

Phylloclades- They are then flattened green stems, with unlimited growth taking over the function of photosynthesis. For example- Opuntia.

Cladodes-In this modification the true leaves are modified into scales or spines, they are green stems of unlimited growth taken over the function of photosynthesis. For example-Ruscus aculeatus.

Modifications of an Underground stem

Sucker- This is an underground non-green special stem, it is present oblique towards its apex. The tip takes an upward bend so that it can produce an upright aerial shoot. For example- Mint

Rhizome- It is generally thick, and grows indefinitely in the soil. Nodes and internodes are differentiated. For example-Ginger, Turmeric

Corm-It is a short, thick, swollen, unbranched, spherical underground stem, which grows vertically in the soil. The aerial shoots manufacture food, and corm stores that food.
For example-Colocasia, Amorphophallus.

Tuber- It represents the swollen end, it is enlarged, devoid of roots, and the surface of the tuber bears several eyes representing nodes. For example- Potato

Bulb- It represents a compact shoot complex, food is stored in scales, leaf bases, and buds. Bulbs are covered by a membranous tunic or remain naked. For example- Onion, Garlic

Final Answer-
 This form of stem undergoes modification to perform functions like storage of food, for help in reproductive growth, and helping plants to survive in unfavorable conditions. Some modifications are also be done to provide mechanical support and protection.