Question

Which one of the following is not an underground modification of a stem?

• A. Rhizome
• B. Runner
• C. Corm
• D. Bulb

Answer 1

The correct option is B Runner

Rhizomes are horizontal underground stems with non-green, fleshy, distinct nodes and internodes. These are brownish in colour and have axillary as well as apical buds. The common types of rhizomes are seen in Alocasia indica, ginger and banana.

Runner: It is a sub aerial modification of a stem that runs horizontally on the surface of the soil. The nodes have scale leaves, adventitious roots and axillary buds. Runners arise from the axillary buds. A large number of runners are produced by mother plants in all the directions. Runners break off and grow into an independent plant. Eg., Cynodon.

Corms are enlarged underground stems that store food for the plant during dormancy. This condensed form of the stem grows in the vertical direction. It is spherical in shape with a flattened base. It has distinct nodes and internodes. Adventitious roots are present either at the base or all over the body. The axillary buds are present on the sides. Eg., Colocasia.

Bulb is an underground stem with fleshy and scale-like layers surrounding a centre bud. The base of the bulb consists of a cluster of adventitious roots. The shoots of the bulbs are developed from the lateral buds and their leaves are capable of storing food. The centre of the bulb contains an apical bud that produces leaves and flowers. Eg., onion and garlic.