Seasonal changes and metabolism of plant hormones in root nodules ofLens sp.

The mature nodules ofLens esculenta Moench. contained higher levels of indolyl acetic acid (IAA), cytokinins (CK), gibberellic acid (GA)-like substances and more active in nitrogenase (N₂-ase) activity than young or old ones. Synthesis of IAA and its metabolism was found to be controlled by tryptophan (tryp) and phenol metabolism, respectively, in nodules of different ages. An abscisic acid (ABA)-like substance being a ‘late growth phase’ hormone, was highest in old nodules. IAA and CK were highest in winter when N₂-ase activity was also highest but then GA and ABA were low. The IAA metabolic pattern of both roots and nodules was regulated by phenols. The hormones hardly changed seasonally in the roots and showed higher activities of IAA oxidase, MeOx reductase, peroxidase and polyphenol oxidase than nodules. The nodular anabolic changes are more pronounced in winter as lentil is a winter crop. The size of nodules at a particular age was the same in different seasons, even though their hormone content varied with the season showing that the nodular hormones were not solely utilized for nodule development and growth.