Justify the following statement on the basis of external features : "Underground parts of a plant are not always roots."

Explanation

Underground parts of a plant are not roots. They may be modified stems for special functions. They may bear stem Like characters, They can be called stems on the basis of following external features.
(a) Presence of nodes and internodes  
(b) Scaly leaves
(c) Axillary and terminal buds
e.g. Rhizome of ginger and banana, corm of Colocasia (Kachalu) and bulb of onion and garlic. etc.