Enhancement of Growth and Endogenous Phytohormones of Azolla pinnata in Response to Tryptophan

Application of tryptophan at different concentrations (0, 5, 15, 30 ppm) to the growth media of Azolla pinnata enhanced growth, N- fixation and endogenous phytohormone levels. Increases of fresh and dry weights as well as doubling time of A. pinnata fronds were generally highly significant with respect to all tryptophan treatments, as compared to corresponding control values at different incubation periods (0, 10, 20, 30, 40 days). Dinitrogenase activity showed an inconsistent increase with elevating tryptophan concentration. The increase in Azolla growth was also concomitant with a noticeable increase in the endogenous content of IAA from zero time up to 40 days. GA3 and ABA were highly increased after 10 days incubation, followed by a gradual decrease afterwards .Generally, IAA, GA3, and ABA hormone levels were higher in response to tryptophan treatments, as compared with those of corresponding controls