Prospection of cyanobacteria producing bioactive substances and their application as potential phytostimulating agents.

This work clarifies some of the substances involved with the biostimulant effect shown by 28 cyanobacteria isolated from different aquatic environments. The production of salicylic acid, cytokinins, siderophores and phosphate solubilization were analyzed , as well as the phytostimulant/phytotoxic effect on watercress seeds at two different extract concentrations (0.5 and 0.2 mg mL). The most prominent plant growth promoting cyanobacteria were verified at two different doses (0.5 and 0.1 mg mL). 21.4 % and 7.1 % of the tested strains produced siderophores or phosphate solubilization, respectively. The production of salicylic acid was stood out for the strains SAB-B797, SAB-B1300 and SAB-M612, while SAB-M251 and SAB-M304 were noticeable regard to cytokinin production. The highest values of germination occurred when the extracts were applied in low dose (0.5 mg mL). SAB-M612 provoked the stimulation of aerial and radicular growth in cucumber seedlings.