Question

define stem modification??Give any 3 examples???​

Answer 1

Answer:

stem modifications means when the stem performs additional functions to adapt different environmental conditions.

examples are rhizome, tuber,bulb,corm, stem tendrils etc

Answer 2

Answer:

In some plants the stems are modified to perform the function of storage of food, support, protection and vegetative propagation.

For food storage: Rhizome (ginger), Tuber (potato), Bulb (onion), Corm (colocasia).

For support: Stem tendrils of watermelon, grapevine, cucumber.

For protection: Axillary buds of stem of citrus, Bougainvillea get modified into pointed thorns. They protect the plants from animals.

For vegetative propagation: Underground stems of grass, strawberry, lateral branches of mint and jasmine.

For assimilation of food: Flattened stem of Opuntia contains chlorophyll and performs photosynthesis.

Underground Modifications

Sub-aerial Modifications

Aerial Modifications

Rhizome

These are non-green with distinct nodes and internodes. There are auxiliary as well as apical buds. These are brownish in colour. The common types of rhizomes are fleshy due to the storage of food material. It also contains terminal buds. E.g., ginger

The rhizome rootstock grows vertically upwards instead of horizontal. Banana and Alocasia indica are some examples of the rhizome.

Bulb

Many fleshy scale leaves are present. The base of the bulb consists of a cluster of adventitious roots. E.g., onion, garlic.

The bulb may be tunicated or scaley. A sheath of dry membranous scale leaves covers the tunicated bulb. A scaley bulb contains no tunic.

Corm

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 auxiliary buds are present on the sides. E.g., Colocasia.

Tuber

It is a fleshy part of the plant which stores food. Potato is the most common tuber largely used as food. The lower part of the potato gets covered by the earth where the adventitious branches grow. It is covered with a number of depressions called “eye” and each eye represents a node. It does not contain adventitious roots. These are largely used as food and grow very slowly.