Page 669 - e-Book

young roots a tryptophan pool was found. Mature root nodules contained higher level of total

phenol than of young roots (Table 2). The IAA might transport from root nodules to other
parts of the plant. It was also expected more free phenols in root nodules of the plants

because the nodules possess higher IAA and lower IAA-catabolising enzyme activity than
roots. Higher quantities of total phenol in the root nodules than young roots would result from

the lower polyphenol-oxidase and peroxidase activity in the root nodules (Stafford, 1974)
than the young roots.

Presence of IAA-metabolising enzymes in both root nodules and roots indicated the

metabolism of IAA in these tissues. The root always contained higher amount of IAA-
oxidase and peroxidise, the IAA-metabolising enzymes, than the root nodules (Table 3). The

presence of higher amount of IAA-metabolising enzymes in roots resulted the lesser amount

of IAA in that tissues. The amount of IAA was controlled as per the necessity by the tissues
accordingly and plays an important role for the persistence of functional root nodules

(Badenoch-Jones et al., 1983).
The activity of the peroxidase and polyphenol-oxidase, two phenol-metabolising enzymes,

were lesser (Table 4) due to the presence of higher levels of total phenols in the root nodules
than the roots (Table 2). As the nodules possess higher IAA and lower IAA-catabolising

enzyme activity than roots, it was also expected more free phenols in root nodules of the

plants.
Higher amount of tryptophan, acts as precursor of IAA, present in the root nodules might be

helped in higher IAA production in those tissues than that of roots. The IAA-metabolising
enzymes, IAA-oxidase and peroxidase might actively control the IAA production in tissues.

The cause of difference of the quantity of total phenol levels in different plant parts would
also be due to the variation in the metabolism and synthesis of total phenols in different plant

tissues by phenylalanine-ammonia lyase and tyrosine-ammonia lyase (Stafford, 1974; Vance,

1978).
The percentage of average organic carbon and total nitrogen were increased as the root

nodules of this plant were mixed up with the soil after decomposition (Table 5). The

percentage of available phosphorus was also increased after decomposition (Table 5). The
percentage of soil moisture was decreased gradually with the gradual decrease of soil depth

from surface level (Table 6).
The organisms present in the nodule have the capacity to increase the organic matter besides

nitrogen fixation. The percentage of available phosphorus changed very little after
decomposition of the root nodules into the soil. It was might be due to the use of the soil

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