CARBOHYDRATE TRANSLOCATION IN ORCHID MYCORRHIZAS

Abstract

The soluble sugars of uninfected regions of Dactylorchis purpurella were found to be glucose, fructose and sucrose. Mycelium of three mycorrhizal fungi, isolated from this orchid, was found to contain glucose and trehalose. Two of the fungi also contained mannitol. Mycorrhizal seedlings of D. purpurella contained carbohydrates contributed by both orchid and fungal partners. The incorporation of 14C into mycorrhizal seedlings was followed, after [14C]glucose had been supplied to infective hyphae some distance from the seedlings. 14C incorporation into soluble and insoluble materials continued throughout the 7‐day experimental period. The results were consistent with the hypothesis that a carbohydrate, possibly trehalose, is translocated by the fungal hyphae into the seedlings. The fungal sugar, trehalose, was the first to become labelled, and the proportion of label in this sugar declined as 14C was incorporated into other carbohydrates, notably sucrose. As sucrose was not found in fungal mycelium, movement of a 14C‐labelled compound from internal fungal hyphae to orchid cells must have taken place. Copyright © 1967, Wiley Blackwell. All rights reserved