Question

In Onion, the swollen underground structure is –
A. Root
B. Rhizome
C. Bulb
D. Tuber

Answer 1

Hint: Underground stems are the plant parts that are modified. They arise from stem tissue. They act as storage tissues for food and nutrients, propagation of new clones and survival. Different forms of underground stems include Bulb, Corm, Rhizome, Stolon, and Tuber. These underground stems are consumed by people including; onion, potato, ginger, yam and taro.

Complete answer:
(A) ROOT - In vascular plants, the roots are the organs of a plant that are modified to provide anchorage for the plant and take up water and nutrients into the plant body. Each root has dermal, ground, and vascular tissues. Types of root systems are:
1. Taproots
2. Fibrous roots
3. Adventitious roots
So, "A" is not the correct answer.

(B) Rhizome - Rhizome, also called creeping rootstalk, horizontal underground plant stem capable of producing the shoot and root systems of a new plant. Rhizomes are simply fleshy underground stems
They grow underground and have eye-like structure similar to those in potatoes.
 Common examples of rhizomes include canna lilies, ginger and bamboo. So, (B) is not the correct answer.

(C) Bulb - In botany, a bulb is structurally a short stem with fleshy leaves or leaf bases that function as food storage organs during dormancy. Bulbs are underground buds with the stem reduced to small discs on which short, fleshy storage leaves grow. These leaves are enclosed by thick scales. Bulb scales morphologically are the continuous sheathing leaf bases. Bulbs are produced by monocotyledons plants in which the usual structure is modified for storage and reproduction. The outer scales are dry and inner scales are generally fleshy and contain reserve food material. For example- onion. So, (C) is the correct answer.

(D) Tuber - Tubers are plant parts that are enlarged to form storage containers that the plants use to hold nutrients that allow them to feed their offspring or to survive through the winter. Two tubers are mainly found. They are the root tubers and stem tubers. Examples of which are potatoes, cassava, and dahlias.
 The fleshy part of the plant stores food. Potato is the most common tuber largely used as food. Its lower part is where the adventitious branches grow. It is covered with bumps or depressions called “eye” and each eye depicts a node. It does not contain adventitious roots. These are largely used as food and grow very slowly. So, (D) is not the correct answer.

Hence, the correct answer is option (C).

Note: Underground stems are modified plants that derive from stem tissue but exist under the soil surface. They function as storage tissues for food and nutrients, propagation of new clones, and perennation Some underground stem modifications are Rhizome, Bulb, Corm and Tuber.