Studies on ectomycorrhizae of pine in an electronically air-filtered, air-conditioned, plant-growth room

Abstract

An air-filtered, air-conditioned, plant-growth room is described and results of initial studies on ectomycorrhizae of pine in the room are presented. The room was fumigated with methyl bromide and maintained free of airborne spores of ectomycorrhizal fungi for 5 months.In the room, loblolly pine seedlings in pots of soil infested with forest humus developed ectomycorrhizae, whereas several hundred control loblolly pine seedlings did not form ectomycorrhizae. Eleven pine species grown in flats of soil infested with either of two isolates of Thelephora terrestris formed morphologically indistinguishable ectomycorrhizae. Noninoculated seedlings of the same pine species did not form ectomycorrhizae but developed dichotomously branched short roots and root hairs.Outside the room, 90% of loblolly pine seedlings grown in pots developed four different ectomycorrhizal forms, regardless of treatment. The 11 species of pine in flats of initially uninfested soil formed abundant ectomycorrhizae with at least two airborne symbionts, one of which was T. terrestris.Large numbers of pine seedlings with and without specific ectomycorrhizal associations can be studied in other than aseptic culture in the room. In this manner, natural forest conditions can be more closely duplicated for studies on ectomycorrhizal versus nonmycorrhizal relationships.