Page 5 - Chapter 14 Reproduction

Examination of a bulb (onion), corm
1 4 > (colocasia), rhizome (ginger) and stem tuber

(potato) and their cultivation to get new plants

Date

There are several types of underground storage organs formed from modified
stem or root. These organs conserve food for the new growth and are also
responsible for the vegetative reproduction in plants. Such energy reservoirs are
all relatively large and fleshy. The main types of underground storage organs are
bulbs, tubers, conns and rhizomes.

A-Bulb of Onion
A bulb is an underground shoot. It consists of a short vertical stem having
adventitious roots with overlapping thick fleshy leaves. A tuft of adventitious
roots arises from the base of the stem. Axillary buds are situated between the
fleshy leaves bases and a terminal (apical) bud lies at the tip of the stem. Axil­
lary buds develop into new bulbs while the terminal bud develops into new
plant.

I

Fleshy Scale Apical • Many onion bulbs
Leaves bud grow from one
onion bulb.
Bulb
Axillary
Stem bud
Adventitious
roots

Fig 14.3: Bulb of onion

Razor, hand lens, pots filled with soil, blade, needle,
bulb (onion), corm (colocasia), rhizome (ginger) stem
tuber (potato)

1. Take a bulb of onion and examine its external
parts.

2. Cut the bulb in half vertically and examine its
internal parts by using hand lens.

3. Record your observations.