Phytohormones and free volatile fatty acids from cyanobacterial biomass wet extract (BWE) elicit plant growth promotion

The present study highlights the importance of cyanobacteria in plant growth promotion and screened the effect of biomass wet extract (BWE 1% and BWE 10%) of twenty cyanobacterial strains on the morphometric parameters of Pisum sativum L. seedlings after germination. Cyanobacterial BWE treatment significantly increased the radicle, plumule and total seedling length along with percentage of response than the control treatment with water. At BWE 1% treatment, Scytonema bohneri MBDU 104 showed 73.3% of the total seedling response, whereas Dolichospermum spiroides MBDU 903 showed increased total seedling length of 5.69 cm among other strains tested. All the tested strains varied among themselves at different parameters. To identify the most potent isolate, all the tested morphometric parameters were evaluated using a multi – criteria decision analysis (MCDA) of PROMETHEE-GAIA software. The isolate Scytonema bohneri MBDU 104 was selected as the potent plant growth promoting cyanobacteria and its BWE was purified using preparative – HPLC and analysed by LC-MS/MS for identifying possible plant growth elicitors. Phytohormones like indole-3 acetic acid (IAA), indole-3 butyric acid (IBA) and cinnamic acid along with free volatile fatty acids were identified and implicated for plant growth promotion by cucumber seed germination bioassay.