Glomus arenarium

Błaszk., Tadych & Madej

SPORES borne singly in the soil or sometimes in roots; orange (5B8) to raw umber (5F8); globose to subglobose; (55-)97(-120) µm diam; sometimes ovoid; 65-105 x 95-140 µm; with a single subtending hypha, rarely with two.

 

SUBCELLULAR STRUCTURE OF SPORES consists of one wall with three layers (swl1-3).

Juvenile and young spores in PVLG+Melzer's reagent
Young (left) and mature (right) spores in PVLG
Mature spore in PVLG
Mature spores in Melzer's reagent

Layer 1 evanescent, hyaline, (0.5-)0.9(-1.5) µm thick before disintegration, closely adherent to layer 2, smooth in juvenile spores, gradually deteriorating and sloughing at the end of formation of layer 2, always absent in mature spores.

Layer 2 flexible to semiflexible (folding when separated from the laminate layer 3), hyaline, smooth, (0.7-)1.1(-1.5) µm thick, sloughing with age, rarely present in mature spores.

Layers 1 and 2 are continuous with a two-layered subtending hypha of juvenile spores.

Layer 3 laminate, smooth, orange (5B8) to raw umber (5F8), (2.0-)6.1(-8.8) µm thick in mature spores, formed by gradual synthesis of very thin, approximately 0.5 µm thick, laminae in the spore and its subtending hypha; the first lamina is highly flexible and frequently separates from layer 2 in crushed spores.

Spore wall layers 1-3 not reacting in Melzer’s reagent.

Layers 1 and 2, when not deteriorated, swell in lactic acid-based mountants. Layer 3 then appears to be covered with blisters or surrounded with an aureola.

SUBTENDING HYPHA hyaline to yellowish white (4A2); straight or recurvate; cylindrical or flared, rarely constricted; (3.7-)4.9(-8.1) µm wide at the spore base.
All in PVLG
Wall of subtending hypha hyaline to yellowish white (4A2); (0.7-)1.1(-1.7) µm thick at the spore base; composed of three layers (shwl1-3) continuous with spore wall layers 1-3 in juvenile spores, then consisting of a single layer continuous with spore wall layer 3.

Pore occluded by a septum, 2.3-4.7 µm wide, continuous with the innermost lamina of spore wall layer 3.

 

 

 

GERMINATION. Not observed.

MYCORRHIZAE. In the field, Gl. arenarium has been associated with vesicular-arbuscular mycorrhizal roots of Ammophila arenaria (L.) Link, Artemisia campestris L., Helichrysum arenarium (L.) Moench., Petasites spurius (Retz.) Rchb., and Senecio sp. (Błaszkowski et al. 2001, 2002a, b; Tadych and Błaszkowski 2000).

The mycorrhizae formed in single-species cultures of this fungal species with Plantago lanceolata L. and Zea mays L. as the hosts were composed of arbuscules, vesicles, and hyphae (Błaszkowski et al. 2001; Błaszkowski, pers. observ.). Arbuscules were numerous and had fine branches difficult to see clearly. Vesicles were ellipsoid, 45-80 x 50-100 µm. Hyphae were (3.7-)6.1(-8.0) µm wide and grew parallel to the root axis. They were straight or slightly curved, sometimes dichotomously branched and frequently coiled. These coils were 18.6-27.3 x 29.7-37.7 µm and evenly distributed along the root fragments examined. In 0.1% trypan blue, arbuscules stained violet white (17A2) to pale violet (17A3), vesicles violet (18A3) to bluish violet (18A7), and intraradical hyphae bluish white (23A2) to pastel violet (17A4).
In roots of P. lanceolata
In roots of Z. mays
In roots of Z. mays

DISTRIBUTION. In Poland, the sites found to harbour Gl. arenarium were maritime dunes adjacent to Swinoujscie (53º55’N, 14º14’E; Błaszkowski et al. 2001), those of the Slowinski National Park (54º45’N,17º26’E; Tadych and Błaszkowski 2000), the Vistula Bar (54º24'N, 19º30'E; Błaszkowski et al. 2002a), and inland dunes of the Bledowska Desert (50º22’N, 19º34’E; Błaszkowski et al. 2002b).

Błaszkowski et al. (2001) found spores of Gl. arenarium in maritime sand dunes adjacent to Tel Aviv, Israel. No data exist of the presence of this fungus in other regions of the world.

NOTES. The only described species of the genus Glomus resembling Gl. arenarium is Gl. etunicatum W.N. Becker & Gerd. The two fungi form spores similar in colour, size and shape with a narrow subtending hypha, whose wall is much lighter-coloured than the wall of its spore. Examination of the spore wall structure easily separates these fungi. The spore wall of Gl. etunicatum consists of a mucilaginous outer layer tightly adherent to a laminate inner layer (Stürmer and Morton 1997). In contrast, the wall of Gl. arenarium spores is composed of a sloughing outermost layer closely associated with a semiflexible middle layer that easily separates from a laminate innermost layer. Although the outermost layers of the two fungi are similar in appearance and quickly slough, the mucilaginous layer of Gl. etunicatum spores stains dark pinkish to reddish purple and that of spores of Gl. arenarium does not react in this reagent. Additionally, the subtending hypha of Gl. arenarium spores is persistent and almost always present in mature spores, whereas that of spores of Gl. etunicatum frequently breaks at the spore base, causing the spores to be similar to those of Acaulospora and Entrophospora spp. when observed at a low magnification.

REFERENCES

Błaszkowski J., Tadych M., Madej T. 2001. Glomus arenarium, a new species in Glomales (Zygomycetes). Acta Soc. Bot. Pol. 70, 97-101.

Błaszkowski J., Adamska I., Czerniawska B. 2002a. Arbuscular mycorrhizal fungi (Glomeromycota) of the Vistula Bar. Acta Mycol. 37, 39-62.

Błaszkowski J., Tadych M., Madej T. 2002b. Arbuscular mycorrhizal fungi (Glomales, Zygomycota) of the Bledowska Desert, Poland. Acta. Soc. Bot. Pol. 71, 71-85.

Błaszkowski J., Tadych M., Madej T., Adamska I., Iwaniuk A. 2001. Arbuscular mycorrhizal fungi (Glomales, Zygomycota) of Israeli soils. Mat. II Polsko-Izraelskiej Konf. Nauk. nt. „Gospodarowanie zasobami wodnymi i nawadnianie roslin uprawnych”. Przeglad naukowy Wydz. Inz. Ksztalt. Srod. 22, 8-27.

Stürmer S. L., Morton J. B. 1997. Developmental patterns defining morphological characters in spores of four species in Glomus. Mycologia 89, 72-81.

Tadych M., Błaszkowski J. 2000. Arbuscular fungi and mycorrhizae (Glomales) of the Slowinski National Park, Poland. Mycotaxon 74, 463-483.