Anatomy of a vesicular—arbuscular endomycorrhizal symbiosis between sugar maple ( Acer saccharum Marsh) and Glomus etunicatum Becker & Gerdemann

Abstract

Microscopic analysis of infection development by Glomus in sugar maple roots revealed changes in the cortical cells similar to those reported by other workers using either herbaceous or woody plant hosts. Few cortical cells contained exclusively terminate hyphal structures. Instead, large intracellular hyphae entered and exited cortical cells while arbuscules formed from initiation points at various places on the intracellular hyphae. Intercellular hyphae were rare and vesicles were not observed. The beaded root morphology observed did not seem to influence the infection process. Beaded roots are formed from repeated constrictions in feeder roots due to major reductions in cell size. The relationship between the constrictions and moisture stress is discussed. The living arbuscule seemed to be the site of transfer between the host and endophyte, implying that the process is an active one.