Distribution and morphology of Neotyphodium endophytes in apical meristems of host plants as observed using differential interference and contrast microscopy

Abstract

Seed transmitted Neotyphodium endophytes colonise the apical meristem (growing point) of young seedlings and later spread into mature leaves and flowers of host plants. However, their location and orientation in the meristems, and the process of their spread into other parts of the plant, are not fully understood. To elucidate this process, the morphology and orientation of mycelia of three Neotyphodium endophytes (N. coenophialum, N. lolii and N. occultans) and their sexual relative, Epichloë typhina were observed using dissected meristem tissues with differential interference contrast microscopy, after chemical clearing. Mycelia of Neotyphodium species more or less ramified in pith or nodal tissue beneath the apical meristem, but were sparsely branched within apical meristems and inflorescences developing from the zone. The distribution of E. typhina mycelia was similar to the Neotyphodium species, but they sometimes appeared on the surface of the merstematic tissues. Keywords: apical meristem, differential interference contrast microscopy, hyphal growth