Sunday, December 20, 2009

study of root modifications-pharma-D-lab manual

study of ROOT modifications

To study different types of root modifications in plants


The organ that is consumed in many vegetable crops, such as carrot and sweet potato, is a modified root that serves as a storage tissue

Tap Root

1. Storage roots
The primary root of tap root become fleshy and swollen due to storage of food. These are of following types:
(a) Conical. Root is broad t the base and gradually tapers towards apex e.g. Raphanus sativus (Radish), Daucus carota (Carrot).
(b) Napiform. The food gets accumulated only in upper parts to give it a top-shaped appearance e.g. Beta vulgaris (beet root) and Brassica napus (turnip).
(c) Fusiform. The root is swollen in middle and tapers towards the base and apex e.g. Raphanus sativus (radish).

Modification of Root System
2. Nodulated tap roots
These are roots modified for N2 fixation. These roots are observed in leguminous plants (pea, gram). These roots bear many small irregular swellings called root nodules. These nodules are living places for nitrogen fixing bacteria, Rhizobium leguminosarum. These bacteria fix and convert free atmospheric nitrogen into nitrates which are absorbed by roots.

3. Pneumatophores or respiratory roots
These are aerial (-ively geotropic) roots or aerophores produced in mangrove plants e.g. Sonneratia, Avicennia, Rhizophora. The underground roots of plants sent out aerial roots or Pneumatophores. These bear several pores or lenticels which help in gaseous exchange.

root modifications of betavulgaris, Daucus carota, raphanus sativus were observed clearly

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