Mycorrhizas of temperate forests

Structure of the Hartig net and establishment of ectomycorrhizas

Studying a variety of field collected mycorrhizas, we clarified for the first time the general three dimensional structure of ectomycorrhizas (Fig. 1) [5].

Fig. 1: Block diagram displaying the Hartig net and the hyphal sheath of ectomycorrhizas [first published in 5].

Fig. 2: Early state of mycorrhiza development in Petri dish cultures (Laccaria amethystina – Picea abies). Photo: I. Kottke.

Using in vitro ECM-cultures (Fig. 2) [10] and TEM-investigations we described the transfer-cell-like ultra structure of the Hartig net (Fig. 3, 4) [11, 6, 19].

Fig. 3: TEM mircograph and scheme of the Hartig net of ectomycorrhizas [Amanita muscaria-Picea abies] displaying active hyphae arranged in a transfer cell- like structure [first published in 11].

We showed that early events in mycorrhiza formation are attachment of hyphae to the suberized root surface followed by splitting off the suberin layer and induction of typical finger like-branching of hyphae (Fig. 4) [60,37].

Fig. 4: TEM micrograph displaying hyphae attaching the root surface and dissolving the superficial suberin layer of the root. Image: I. Kottke.

Previously, we found that contact of hyphae to the root surface induced reduction of soluble and cell wall bound phenolics facilitating ingression of hyphae between the root cell walls (Fig. 5) [15].

Fig. 5: Cell wall bound, fungi-toxic ferulic acid is lowered in mycorrhizal roots [HPLC analysis; first pubished in 15].

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Description of ectomycorrhiza morphotypes

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