Hyphal Mantle Research Articles

Tuberculate mycorrhizas of Castanopsis horneensis King and Engelhardtia roxburghiana Wall

summaryTuberculate mycorrhizas of Castanopsis borneensis King (Fagaceae) and Engelhardtia roxburghiana Wall. (Juglandaceae) were studied by light and electron microscopy. The tubercles of both trees showed similar structure and morphology. The fungal partner is an unidentified basidiomycete. Beside normally developed mycorrhizas in each tubercle some heavily‐infected roots were found. These roots are characterized by a very thick hyphal mantle around a dead root tip and a circle‐like ingrowth of the fungus up to the vascular tissue – the strangulation zone. All cells distal to the strangulation zone were dead, but basipetal to it, normal cortical tissue with an epidermal Hartig net was present. The outer cortex in this region showed wall ingrowths along the inner tangential walls and an accumulation of ER and mitochondria. The formation and function of the heavily‐infected roots is discussed.

Some distinctive types of spruce mycorrhizae

For examination and recognition of mycorrhizal types, the structure of the hyphal mantle in tangential longitudinal sections has proved to be a valuable feature for investigation. Features of hyphal mantle structure have been used for establishing an identification key. The colour of the hyphal mantle is a helpful additional characteristic, but is not useful as a diagnostic feature because of variations in advanced age and under varying environmental conditions. Rhizomorphs yield good taxonomic characteristics. The Hartig net was uniform for all types examined. When differences were observed they had to be interpreted as different stages of development. Ultrastructural examination revealed further features of mycorrhizal types: namely the shape of septal pores, presence and structure of matrix material in the region of the hyphal mantle and characteristic deposits on cell walls of the hyphae. The ten types presented can be distinguished without any ultrastructural features. As far as the fungal partners involved are concerned, basidiomycetes are clearly dominant. For the first time two basidiomycetes with continuous parenthesomes of their dolipores were found to form ectomycorrhizae. Classification of these fungi with the heterobasidiomycetes is discussed.

Hartig net structure and formation in fully ensheathed ectomycorrhizas

The structure and formation of the Hartig net was examined in four different types of spruce ectomycorrhizas from the field. The investigations confirmed that in the case of mycorrhizas with a fully developed sheath enclosing the root apex, the Hartig net is formed by a highly branched fingerlike or puzzlelike hyphal system.It is shown that the hyphae penetrate and grow mainly in a transversal direction to the axis of the root, resulting in typical indentation patterns on some tangential walls and a fountainlike separation of hyphae when growing from the radial to the tangential intercellular spaces. Septae formation within the branched hyphal system of the Hartig net is rare. Structures which, in sections, appear to be incomplete septae are explained as the result of the branching pattern.The alignement and the typical branching pattern of the Hartig net is also found around the outermost cortical cells. A description of the changing structure in the different layers of a pseudoparenchymatous hyphal mantle is given. Finally, details of the three‐dimensional structure of the mantle and the Hartig net are represented in a block diagram.

The ultrastructure of the zygospore in Endogone flammicorona Trappe & Gerdemann

The ultrastructural organization of the spores of the sporocarp of Endogone flammicorona was studied. Two types of organization are described. Initially the spore possessed a vacuolate protoplasm and was bound by two cell wall layers. The spore was surrounded by a hyphal mantle formed of a sheet of vacuolized hyphae with uniformly thin walls. Secondly, although the ultrastructural features of the spore appeared the same, it was now surrounded by a hyphal mantle with unevenly thickened walls (i. e., the so-called flaming crown) due to the gradual and irregular deposition of granules and lamellae. This crown gives the spore its most commonly observed morphological feature and is the preminent character employed taxonomically to speciate Endogone flammicorona Trappe & Gerdemann.