Endogenous auxins in plant growth-promoting Cyanobacteria-Anabaena vaginicola and Nostoc calcicola

Three isolates of heterocystous cyanobacteria, belonging to the genera Anabaena and Nostoc, gathered from Iranian terrestrial and aquatic ecosystems exhibited considerable growth promotion effect on several vegetables and herbaceous plants. To study the ability of these three isolates to produce auxins, three endogenous auxins, including indole-3-acetic acid (IAA), and two of its main homologues, indole-3-propionic acid and indole-3-butyric acid, were extracted and analyzed with high-performance liquid chromatography equipped with diode array detector and fluorescence detector, and the results were further confirmed with liquid chromatography-tandem mass spectrometry (LC-MS/MS) in the negative-ion mode. The dominant auxin observed in all isolates was indole-3-butyric acid (IBA) in the range of 140.10-2146.96 ng g(-1) fresh weight (FW), and only small amounts of IAA (2.19-9.93 ng g(-1) FW) were detected. The predominance of IBA in these strains is reported for the first time which is different from the previously reported auxin profiles in microalgae and algae with the predominance of IAA.