UPTAKE OF [14C]GLUCOSE BY ASYMBIOTIC AND MYCORRHIZAL ORCHID PROTOCORMS

Abstract

SummaryIn cultures of Goodyera repens Br. infected with its natural mycorrhizal endophyte, Ceratobasidium Cornigerum (Bourdot) Rogers, 14C supplied as glucose reached a peak in the external mycelium within 48 h but accumulated in protocorms over several days. Uptake directly from the substrate into non‐infected protocorms was much slower with less incorporation of 14C into insoluble material than occurred in infected protocorms. There was a similar pattern of uptake from two Ceratobasidium spp. into Dactylorhiza purpurella (T. & T. A. Steph) Soó but the amount of glucose accumulated was less using a natural endophyte than with an isolate originally obtained from rice plants. Using an un‐named Cymbidium hybrid in symbiosis with Ceratobasidium sp. from D. purpurella, there were low rates of uptake into both non‐infected and infected protocorms. 14C from glucose appeared in mannitol and trehalose in mycelium but mainly in glucose, fructose and sucrose in the orchid, with traces of trehalose in infected tissue. In freshly‐infected protocorms, only trehalose became labelled in the pre‐digestive phase of infection and there was no evidence of transfer of 14C from fungus to host before digestion of hyphae occurred.