A comparative effect of IAA and 4-Cl-IAA on growth,nodulation and nitrogen fixation in Vigna radiata (L.) Wilczek

The plants of mung bean (Vigna radiata L. Wilczek) were raised from the seeds soaked in water (control), IAA or 4-C-IAA (10⁻⁶, 10⁻⁸ or 10⁻¹⁰ M) for 8 or 12 h. The plants were allowed to grow in a net house and were sampled at 30 and 45 days after sowing (DAS). Both IAA and 4-Cl-IAA significantly affected the growth (length, fresh and dry mass of roots and shoots), the number of nodules, their fresh and dry mass and the activity of nitrogenase. However, the contents of nitrogen and carbohydrate exhibited a decrease in response to both the auxins. 4-Cl-IAA, at a concentration of 10⁻⁸ M, generated the best response. Moreover, 4-Cl-IAA at other two concentrations (10⁻⁶ and 10⁻¹⁰ M) was much more active than any of the IAA concentration used.