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Metabolism Of Indole Acetic Acid Within The Root Nodules And Changes

Of Edaphic Factors In The Rhizospheric Area Of Vigna Radiata

Sisir Ghosh *

Assistant Professor, Department of Botany, Sreegopal Banerjee College, Bagati, Mogra,
Hooghly-712148, West Bengal, India

* Email of corresponding author: sisirghosh1981@gmail.com

ABSTRACT
The mature root nodules of Vigna radiata (L.) R. Wilczek (Mung bean), a pulse legume,

contained higher amount of indole acetic acid (IAA) and total phenol than non-nodulated
roots. Higher amount of tryptophan pool both in the root nodules and the roots were found as

the precursor molecule of IAA. Presence of IAA oxidase and peroxidase, the IAA
metabolising enzymes, in the nodules and roots indicated the metabolism of IAA in the

nodules and roots. Metabolism of phenol by enzymes in both root nodules and roots

controlled the IAA production in those tissues. Decomposition of the mature root nodules
were increased the percentage of average organic carbon and total nitrogen over control as

the root nodules were mixed up with the soil after decomposition. The important
physiological implications of the IAA production and the changes of edaphic factors of the

rhizospheric area in the light of legume-Rhizobium symbiosis were discussed.
KEY-WORDS

Vigna radiata, root nodule, indole acetic acid, edaphic factors, symbiosis

INTRODUCTION
Leguminous plants (under the family Fabaceae), which belong to the third largest (after

Orchidaceae and Asteraceae) family of angiosperms (Mabberley, 1997), include
approximately 765 genera and about 20000 species worldwide (Christenhusz and Byng,

2016). The rhizospheric area of the leguminous plants contain plant growth promoting

rhizobacteria (PGPR), that are able to colonize the rhizospheric area including the roots
(Azhrafuzzaman et al., 2009) and promote growth by direct or indirect mechanisms

(Widowati et al., 2019). Rhizobia, which include more than 98 species within 14 genera
(Berrada and Fikri-Benbrahim, 2014), are bacteria capable of fixing atmospheric nitrogen and

forming root nodules in plants of the family Fabaceae. Only 20% of the leguminous plants

have been examined for nodulation (Hopkins, 1999) and only 0.5% of the legumes have been
studied in relation to the nodule bacteria (Jordan, 1984). Different phytohormones in variable

amount detected by different researchers in the root nodules act important roles in genesis

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