Modifications of Underground Stems

The stem is essential for plants as it:

• Provides support
• Transfers nutrients and water from roots
• Transfers food from leaves to different parts of the plant

Overview of Underground Stems

• While most stems grow above ground, some grow underground to store food.
• Above-ground stems are typically long, while underground stems are swollen and thick.
• Underground stems have definite growth and serve various functions.

Types of Underground Stems

There are four main types of underground stems:

1. Rhizome

• Definition: An underground, horizontal stem with nodes and internodes.
• Features:
  • Has scale leaves at the nodes.
  • Irregular shape.
  • Can give rise to new stems and leaves through buds.
• Examples: Ginger, Turmeric.

2. Corm

• Definition: A rounded underground stem that is flattened at the top and bottom.
• Features:
  • Condensed form of rhizome; spreads less than rhizome.
  • Bears one or more buds in the axils of scale leaves.
• Example: Asia.

3. Tuber

• Definition: An enlarged, spherical underground stem that stores food.
• Features:
  • Has many dormant buds on its surface known as "eyes."
  • If a part with a bud is planted, it can grow into a new plant.
• Example: Potato.

4. Bulb

• Definition: A condensed, disk-like stem that stores food in fleshy leaves.
• Features:
  • Composed of two types of leaves:
    1. Fleshy leaves
    2. Scaly leaves
  • Upper part has a terminal bud covered by scaly leaves.
  • Inner fleshy leaves store food.
• Example: Onion.

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This summary highlights the modifications of underground stems and their classifications along with examples.