Page 4 - Lesson Notes-Morphologyof flowering plant

(e) Nodulated Tap Roots In this the secondary, tertiary and sometimes primary roots
bear many small irregular swellings called root nodules which contain countless,
minute nitrogen fixing bacteria of the genus Rhizobium, e.g., groundnut (Arachis
bypogea), clover (Medicago falcata), pea (Pisum sativum), etc.
(f) Pneumatophores These are special roots that develop in mangrove plants (grow
in marshy areas). The pneumatophores or aerophores or respiratory roots grow
vertically upward and are negatively geotropic.
They have minute breathing pores called pneumatophores or lenticels present on the
tips of vertical roots that help in getting oxygen for respiration.
Modification of Adventitious Roots
The adventitious roots are modified to perform several additional functions like food
storage, mechanical support and other vital functions.
(a) Fasiculated Roots These arises in clusters from the base of the stem, e.g., Dahlia,
Asparagus.
(b) Nodulous Roots These roots have swellings occur only near the tips, e.g., Arrow
root (Maranta), amia haldi (Curcuma amadd).
(c) Tuberous Roots (Single Root Tubers) These are swollen without any definite
shape, e.g., Ipomoea batatas (sweet potato).
(d) Prop (Pillar) Roots The prop roots grow as the horizontal branches of the stem
and grow vertically downward.
They become thick pillar-like and provide mechanical support to the giant trees, e.g.,
Banyan tree (Ficus benghalensis).