photobiont UK /ˌfəʊ.təʊˈbaɪ.ɒnt/US /ˌfoʊ.toʊˈbaɪ.ɑnt/ noun1 •A photosynthetic symbiont, especially those in symbiosis with fungi in lichen.It has micobiont from Ascomycota and Basidiomycota belonging to kingdom Fungi and photobiont from Trebouxia species. — 2022 formsphotobionts