Morphology and ecology of arbuscular and orchid mycorrhizas

Abstract

Arbuscular mycorrhiza (AM) is morphologically divided into two types, Arum and Paris type. The Arum type was dominantly found in herbaceous plants in a vacant land and seedlings of pioneer woody plants in an oil palm plantation, whereas the Paris type was dominant in understory plants in deciduous broadleaved forests. These results suggest that the Arum type could be advantageous to the fast-growing plants, while the Paris type is advantageous to slow growers in shaded condition. A mycorrhizal fungus of an achlorophyllous plant Sciaphila tosaensis forming hyphal coils was revealed to be Glomus sp. by molecular analysis. The hyphal coils of mycorrhizal fungi are also formed in orchid mycorrhiza (OM) . It was first shown in this study that Coprinus spp. and Psathyrella spp. in Coprinaceae form OM in an achlorophyllous orchid, Epipogium roseum. In OM of achlorophyllous orchids, it is considered that nutrients including carbon compounds are transferred from mycorrhizal fungi to plants. It was interesting that morphologically common feature to form hyphal coils to be lysed is found in the two different mycorrhiza, AM in S tosaensis and OM in E roseum, having the same function to transfer carbon compounds from the mycorrhizal fungi to the host plant.