Anti-cyanobacterial allelopathic effects of plants used for artificial floating islands

This study aimed to identify the plants suitable for artificial floating islands. We screened the 7 plants spp. [Canna (Canna generalis L.H.Bailey), grassy-leaned sweet flag (Acorus gramineus Sol. ex Aiton), lesser bullrush (Typha angustifolia L.), purple loosestrife (Lythrum salicaria L.), reed (Phragmites australis (Cav.) Trin. ex Steud.), softstem bulrush (Scirpus tabernaemontani Gmel.) and yellow iris (Iris pseudacorus L.)] showing the anti-cyanobacterial allelopathic effects through release of anti-cyanobacterial compounds from their roots. To determine their potential anti-cyanobacterial allelopathic effects, we prepared methanolic extracts from the roots and investigated their effects on growth of cyanobacterium Microcystis aeruginosa. We found that I. pseudacorus, A. gramineus, T. angustifolia, S. tabernaemontani and P. australis had anti-cyanobacterial compounds in their roots. The culture solutions from these plants were used in cyanobacterial assays, which showed that only T. angustifolia, S. tabernaemontani and P. australis released anti-cyanobacterial compounds from their roots. Thus T. angustifolia, S. tabernaemontani and P. australis are potential beneficial species for vegetation on artificial floating islands. These species may enhance the water purification owing to anti-cyanobacterial allelopathic effects.