Zahra Fallah hosseini - Department of Plant Sciences and Biotechnology, Faculty of Life Sciences and Biotechnology, Shahid Beheshti University, Tehran, Iran.
Hossein Riahi - Department of Plant Sciences and Biotechnology, Faculty of Life Sciences and Biotechnology, Shahid Beheshti University, Tehran, Iran
Majid Ghorbani Nohooji - Medicinal Plants Research Center, Institute of Medicinal Plants, ACECR, Karaj, Iran
Zeinab Shariatmadari - Department of Plant Sciences and Biotechnology, Faculty of Life Sciences and Biotechnology, Shahid Beheshti University, Tehran, Iran

Cyanobacteria have the ability to nitrogen fixation, and the production of plant growth-stimulating substances, which increases plant growth and productivity as biological elicitors. Considering the medicinal value of Echinacea purpurea (L.) Monch, the effect of two species of heterocystous cyanobacteria, Nostoc punctiforme Hariot and, and Nostoc calcicola Brébisson ex Bornet & Flahault, on growth factors and phenolic content of this medicinal plant were evaluated. For this purpose, four pots were considered for each treatment and four others for the control plants. E. purpurea cultivated in a randomized complete block design in an experimental greenhouse condition. Then the treated plants were irrigated with ۱۲۰ ml of ۰.۲% cyanobacterial suspensions at ۲۰-day intervals. After ۶۰ days, plants were collected and dried under shade and at room temperature. The total phenolic content of the aerial part and root of treated and control plants were evaluated using the Folin-Ciocaltiu method. The results showed that the total phenolic content of cyanobacterial-treated plants, especially plants treated with N. calcicola, significantly increased. This metabolite improvement was observed both in the aerial part and the root system of the N. calcicola treated plants. The results also showed that plant growth parameters such as root and stem length, as well as number of leaves in both treatments increased significantly compared to the control. As a result of this study, cyanobacteria can be improving the phenolic content and growth indices of the medicinal plant E. purpurea.

Cyanobacteria, Echinacea purpurea, Secondary metabolite, Bioelicitor, Nitrogen fixation