Mycorrhizas of temperate forests

Ecology of ectomycorrhizas and potential toxic elements

We analyzed ecotmycorrhizas using two techniques:

	Vital fluorescence staining
	Electron energy loss spectroscopy and imaging (EELS/ESI)

Vital fluorescence staining

Ectomycorrhizas in temperate forests were found to display important growth dynamics [6, 1], and active and declining stages can be displayed by vital fluorescence, (Fig. 1) [44, 42, 9].

Fig. 1: Staining by Fluorescein-diacetate reveals active hyphal sheath and Hartig net hyphae of ectomycorrhiza formed by Xerocomus badius-Piceae abies [courtesy of T. Ritter].

Electron energy loss spectroscopy and imaging (EELS/ESI)

Free, toxic aluminium ions were hypothesized by several authors to cause forest decline but were shown by us to be strongly bound in polyphosphates that accumulate in the hyphal vacuoles [28,27] (Fig. 2, 3).

Fig. 2: Foto: ESI micrograph revealing P and Al in the same precipitations of hyphal vacuoles [first published in 28].

Fig. 3: EEL-Spectra proving the two elements, P and Al, in situ [TEM 902, Zeiss]. [first published in 28]

Instead, mycorrhizas were found to be endangered and damaged by high nitrogen input, because accumulation in the fungal vacuoles significantly reduced glycogen storage (Fig. 4, 5) [47, 31].

Fig. 4: ESI micrograph displaying nitrogen accumulation in vacuoles of fungi exposed to elevated ammonium in the nutrient solution Image: I. Kottke.

Fig. 5: Graph displaying correlation between amounts of nitrogen containing bodies in the vacuoles and glycogen granules in the cytosol of hyphae of the mycorrhizal sheath. Plants were exposed to low and elevated N concentration in the substrate and to normal and doubled CO2  in the atmosphere [first published in 47].

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Ectomycorrhizas for sustainable forests

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