The stems get modified to perform various functions and lack green colour due to its geophilous nature and grow under the ground and identified by the presence of nodes, internodes, scale leaves, buds and branches.
These are of various types:
Sucker: The - sub aerial branch that arises from the main stem and it grows initially grows horizontally below soil later grows obliquely upward. Examples are Mentha arvensis.
Stem tuber: The tuberous tip of an underground branch. The axillary branches that are produced near the soil surface grow into the soil and their tip becomes swollen due to the accumulation of starch. The example is Solanum tuberosum.
Rhizome: Its is a thick, underground dorsiventral stem that grows horizontally at a particular depth within the soil. The example is Ginger.
Corm: It is the underground modification of the main stem with more diameter than length. It stores food materials and become tuberous. The example is Colocasia.
Bulb: A specialized underground stem which bears roots in its lowers sides and rosette of leaves on the upper side. The leaf bases or scales become fleshy due to the accumulation of food. The example is Allium cepa.
Modifications of stem for:
- (a) storage
- (b) support
- (c) protection
- (d) spread and vegetative propagation
