Modification of the Underground Stem - Practice Questions & MCQ

Modification of the Underground Stem

• Underground stem may appear to be root but show features of stem like distinct nodes and internodes.
• They bear scaly non-green leaves with axillary buds.
• These act as organ of perennation and storage of food.

Rhizome

• It is fleshy, non-green, underground stem.
• There is a clear demarcation of nodes and internodes.
• They have terminal bud as well as axillary bud.
• Axillary buds are present in the axils of each scaly leaf. 
• They can give rise to new shoots.
• For example, Ginger, turmeric, banana, etc.

Stem Tuber

• Stem tubers are swollen underground branches (stolons).
• These are swollen due to storage of food.
• These are covered with corny skin and small depressions called eyes.
• Each eye represents node.
• These can sprout and produce new shoots.
• They lack adventitious roots.
• For example, potato

Bulb

• These are highly condensed discoid stems.
• The upper surface is conical and bears apical bud.
• There are numerous scaly leaves which store food.
• When scaly leaves surround the apical bud in the form of concentric rings, it is called tunicated bulb, for example, onion.
• When scaly leaves partially surround the apical bud, it is called scaly bulb, for example, garlic.
• From the lower surface, adventitious roots arise.

Corm

• It is condensed rhizome which grows vertically downwards.
• It has a flattened base.
• There are distinct circular nodes and internodes.
• The scaly leaves and axillary buds arise from the nodes.
• Adventitious roots may arise at nodes or all over the body.
• For example, colocasia, zaminkand (yam), saffron, etc.