Stem - Modifications

Description:

Stems undergo modifications in order to perform additional function like storage, support, vegetative propagation etc.

The modifications are −

Food Storage

• Underground stems are modified to store food. E.g. Potato, ginger, turmeric etc.
• They act as organs of perennation. They help in the survival of the plants under unfavourable conditions.

Stem tendrils

• Develop from axillary buds.
• Slender, spirally coiled.
• Help plant to climb. E.g. cucumber, pumpkin etc.

Thorns

• Axillary buds of stem may get modified into woody, straight and pointed structures called thorns.
• Found in plants such as Citrus, Bougainvillea etc.
• They protect plants from grazing animals.

Phylloclade

• Green, flattened or cylindrical stem.
• It takes the form and function of a leaf.
• They contain chlorophyll and hence perform photosynthesis.
• Mostly found in xerophytic plants where leaves grow feebly or fall off early.
• E.g. Opuntia, Euphorbia etc.

Runners

• It has a creeping stem with long internodes.
• They can grow in all directions and spread to new niches.
• When older parts die the branches separate from parent plant and form independent plants.
• E.g. Grass.

Sucker

• Sucker are like runners.
• A slender lateral branch arises from the base of the main axis.
• It grows aerially for some time then arch downwards to touch the ground.
• E.g. Mint.

Stolon

• Slender lateral branch which appears from the lower part of the main axis.
• This lateral branch grows aerially for some distance and becomes arched and finally touches ground to give rise to new shoot.
• They bear roots to get fixed to the soil.
• E.g. Jasmine

Offset

• Usually found in aquatic plants.
• Bears a cluster of leaves near the water or ground level and gives adventitious roots inside water or ground from all nodes.