Question

Type of stem structure present in Colocasia is
a. Corm
b. Bulb
c. Rhizome
d. Tuber

Answer 1

Hint: Stems are the ascending part of vascular plants. They have multiple functions like providing and storing nutrition, transport of water and minerals from roots to other parts and formation of new tissues.

Complete answer:
The stem of a particular plant is often specialized to support the needs of the plant. Let us discuss the types given in the options:
> Corm – These, also known as bulbotuber, are underground stems that facilitate food storage. As the name ‘bulbotuber’ suggests they are fleshy, long and swollen. Such a feature enables the plants with this type of stem to survive in winters as well as in hot temperatures. Along with this, corm has one or more internodes, which has at least one growing point. Thus, the plant can be propagated and distributed by planting a properly treated corm. Example: Taro (belongs to Genus Colocasia), crocus.

> Bulb – These are shortened stems that are fleshy, layered, bulb shaped stems which stores food and helps plants survive dormancy. The central part of the bulb contains the vegetative growing point and the base has reduced root structure. The bulb, if surrounded by dry membranous outer scales, are called tunicate bulbs. Example: Onion, garlic. Otherwise, they are called non-tunicate bulbs. Example: Lilium, Fritillaria.

> Rhizome – They have horizontal underground stems whose primary purpose is to produce new plants and it also stores food. With the presence of short internodes, the rhizome gives rise to the shoot system upwards and roots grow downwards. Example: Turmeric, ginger.

> Tuber – These are formed when the rhizome thickens. Therefore, they have similar characteristics and functions as rhizomes. These stem tubers are not to be confused with root tubers. The root tubers are modified forms of lateral root. However, they have the same function and appearance as stem tubers. Example: Potatoes, cassava.

Hence, the correct answer is option (A).

Note: The stems can be either underground or above the ground. The underground storage stems such as bulbs, tubers and corms can be categorised as geophytes. Other bulb structures above the ground (epiphytic) are called pseudo bulbs, as they resemble bulbs.