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Vesicular-arbuscular mycorrhizas in Italian sand dunes
552
Notes and brief articles
DENNIS, R . W . G . (1961). Some inoperculate discomycetes from New Zealand. Kew Bulletin 1S, 293-320 . KOHN, L. M . & KORF, R. P. (1975). Variation in ascomycete iodine reactions : KOH pretreatment explored. My cotaxon 3, 165-172. KORF, R . P. (1973). Discomycetes and Tuberales, In The Fungi, vol. IVA (ed. G. C. Ainsworth, F. K. Sparrow &
A. S. Sussman), pp. 249-319. New York and London: Academic Press . RAITVIIR, A. (1970). Sy nopsis of the Hyaloscypha ceae. Tartu : Academ y of Scien ces of the Estonian S.S.R . SEAVER, F . J. (1951). The North AmerIcan Cup-Fungi iinoperculates), New York.
VESICULAR-ARBUSCULAR MYCORRHIZAS IN ITALIAN SAND DUNES BY MANUELA GIOVANNETTI
Centro di Studio per la Microbiologia del Suolo, C.N.R., Via Borghetto 80, 56100 Pisa, Italy AND T. H. NICOLSON
Department of Biological Sciences, University of Dundee, Dundee DD1 4HN, Scotland
Ecological and taxonomic studies on vesiculararbuscular mycorrhizas (VAM) were initiated in Italy with the pioneer work of Peyronel (1923-24, 1937). He recorded this form of mycorrhiza in a wide variety of plants from different habitats and communities, and presented the first evidence that the endophytes belonged to the Endogonaceae. Subsequently, extensive ultrastructural studies on VAM have been carried out (Scannerini & Bonfante-Fasolo, 1979; Bonfante-Fasolo et al., 1981) but there has been little work on the ecological and taxonomic aspects of Italian endomycorrhizas. There is now considerable interest in mycorrhizas of sand-dune communities (N icolson & Johnston, 1979; Koske & Halvorson, 1981 ) and this paper records VAM in dune plants in Tuscany on the west coast of Italy. Five replicate samples of roots and rhizosphere were collected in 1980 from each of 18 angiosperms from localities near Follonica (approx. 42° 55 ' N), Migliarino and Alberese (100 km Nand 40 km S of Follonica respectively). The vegetation sucession varied considerably on these three dunes. At Migliarino there was a stable dune system, some 200 m wide, with an extensive and varied flora (Arrigoni, 1981). At the other more southerly sites the dunes were short and eroded with a paucity of higher plants. Only three species, including the dune grass Ammophila arenaria were present in all 3 sites, although a number of others were common to two sites (Table 1). Staining of the root samples (to g fresh weight for each species) was by the technique of Phillips & Hayman ( 1970) and quantitative assessment was by the grid-line intersect method (Giovannetti & Mosse, 1980) to obtain per cent root infection. Endogonaceous spores and sporocarps were extracted from 100 g samples of sand by wet-sieving and decanting (Gerdemann & Nicolson, 1963 ) down to Tram . Br . mycol . Soc. 80 (3) (1983)
a mesh size of 45 um . Of the 18 species examined from the 3 sites VAM was found in all except Cakile maritima and Convolvulus soldanella (Table 1). Mean percentage infection varied greatly with site and species . Over 60 % infection occurred in only a few plants, but species of the cosmopolitan families Gramineae, Papilionaceae and Compositae were heavily infected. The morphological appearance of the infections was highly variable with regard to the presence of arbuscules and vesicles . No doubt such differences were related to the host / endophyte combination and influenced by seasonal and edaphic factors. It was not surprising to find no infection in Cakile maritima as it is in a family generally considered to be non-mycorrhizal (Gerdemann, 1968). However, VAM did occur in two Silene spp. (Caryophyllales, Centrospermae) which are likewise reputed to be non-mycorrhizal. Mycorrhizal absences in these specific groups may not always be the rule (H irrel, Mehravaran & Gerdemann, 1978). Large amounts of rhizosphere mycelium were frequently present particularly on roots of Ammophila arenaria, Eryngium maritimum and Helichrysum stoechas. This was typically endogonaceous, showing characteristic angular projections. It frequently entangled sand grains and fragments of organic debris and attached them to root surfaces. Clearly, this mycelium was an important factor in sand aggregation as has been found for other dune systems (Forster, 1979; Forster & Nicolson, 1981; Koske , Sutton & Sheppard, 1975 ; Sutton & Sheppard, 1976). Also abundant on the roots and in sand was mycelium of a brown septate nature, which may belong to the fungus Phialophora radicicola var. graminicola (N icolson & Johnston, 1979).
The variation in appearance of infections indicated that a number of endophyte species were
Primed in Great Britain
Notes and brief articles T able
1.
553
M ean percentage root infec tion (and range) of V AM in thr ee sand dunes in Tu scany
Plant species
M igliarin o
Follonica
Alberese
Ammophila arenaria (L. ) Link (Grarnineae) L agurus ovatus L. (G rarnineae) V ulpia ligustica (All.) L ink (Grarnineae) Medicago marina L. (Leguminosae) M . littoralis Rohde ex Loisel. (L eguminosae) On onis oariegata L. (L egumin osae) Anacyclus radiatus Lo isel. (Compositae) Anthemis maritima L. (Compositae) H elichrysum litoreum Gu ss. (Compositae) H . stoechas (L.) Moen ch (Compositae) S ilene colorata Poiret (Cary ophyllaceae) S. otites (L. ) Wibel (Caryophyllaceae) Cak ile maritima Scop . (Cruciferae) Convolv ulus soldan ella L. (Convolvulaceae) Eryngium maritimum L. (Umbelliferae) Euphorbia paralias L. (Euphorbiaceae) Pancratium maritimum L. (Amaryllidaceae) Rosmarinus officinali s L. (Labiatae)
18 (10-70)
24 (20-30) 7 (5- 20) 12 (0-20)
24 (0-40)
pr esent , and this was confirmed when spore populations were examined. The numbers of spores also varied greatly with the highest being on the roots of H elichrysum stoechas. H owever, numbers of spores did not appear to be related to amounts of infection . For instance, Vulp ia ligustica from the Albere se site showed 62 % root infection, but no spores were recovered. Identification and classification of endophytes (after Gerdemann & Trappe, 1974 ) has been almost entirely from field material and more positive identifications must await the successful establishment of pot cultures. Chlamydospores and sporocarps of 4 Glomus spp. and 2 Sclerocystis spp . were observed, but only two of the Glomus spp . were positively identified : ( 1) Glomus mosseae (N ieol. & Ger d.) Gerdemann & Trappe. This species was mostl y recovered as ectocarpic chlamydospores which showed a dist inctive long funnel-shaped attachment (Fig. 1). This is similar to a form of G. mosseae which has been reported from Libya (El-Giahmi, Ni colson & Daft, 1976 ), from Australia (Mosse & Bowen, 1968) and the Pacific northwest of U.S .A. (Gerdemann & Trappe, 1974). The constancy of appearance and its occurrence here and in other parts of the world may mean that this form merits a new taxonomic status. (2) Glomus [asciculatum (T haxter sensu Gerdemann) Gerdemann & Trappe. This, one of the commonest and most variable ofendophyte species, was pre sent in the form of loose sporo carpic clusters up to 3 rom diam (Fi g. 2) varying in colour from light to dark brown. The individual chlamydospores were 20--90 pm diam when globose but irregular-shaped spore s had dimens ions of up to Trans. Br. my col. S oc. 80 (3) (1983)
62 (40-80)
12 (10-20) 72 (60-90) 10 (0-20) 28 (10-40) 48 (30-70)
40 (30-50) 26 (10-50)
36 (30-60) 2 (o-to) 16 (5- 20)
° ° 34 (20-50)
0 0
38 (30-50)
0 68 44 72 2
°
(60-80) (40-50) (6<>-90) (o-to)
Distinctly different from the above was another type of sporocarp 1-2 rom diam conta ining more than 50 chlamydospores which were 70-100 pm , hyaline to light yellow. These spores possessed a very distinct wall of two layers, both 4-5 pm th ick, the outer being hyaline and the inner yellow (F ig. 3). This fungus could also be classed as G. [as ciculatum as presently constituted (Gerdemann & Trappe, 1974 ). Pot cultures will be necessary to indicate whether it might be a different species. A further Glomus sp. has sporocarps 250-400 pm diam containing 8-24 brown spores with dimen sions 30-60 pm and single wall 5 pm th ick. This fungus was only present at the Miglia rino site where it reached up to 95 spores 100 g-1 in H . stoechas samples . It could be considered as a non-peridial form of G. microcarpum. These observations emphasize the difficulties, stressed by Gerdemann & Trappe (1974), of dealing with the G. microcarpum-fasciculatummacrocarpum complex where the criterion for species separation is mainly the size of the chlamydospores. Two species of the azygosporic genus G igaspora were widely distributed in the dune samples , one being hyaline and th e other pigmented. The former is Gigaspora calospora (N icol. & Gerd.) Gerdemann & Trappe with subglobose azygospores 182-260 pm in size. The wall is 5 pm thick with a smooth out er surface. The spore and its suspensorlike bulbous attachment (Fig. 4) are the same white-cream colour , this being a characteristic feature of G. calospora (Gerdemann & Trappe, 1974). Att empts at pot culturing this species with
108 pm.
Pr int ed in Gr eat Britain
Notes and brief articles
554
2
3 Fig.
1.
Glomus mosseae. Note the funnel-shaped attachment. (Bar =
Fig. 2 . Sporocarps of Glomus [asciculatum. (Bar
100
pm )
= 50/tm )
Fig. 3. Chlamydospores from a sporocarp of a Glomus sp ., showing the two-layered wall. (Bar =
10 flm )
Fig. 4. Gigaspora calospora . Note that the azygospore and its attachment are concolourous. (Bar = 50 pm)
Medicago sativa have not yet been successful so the
singly-formed accessory vesicle stage, which would provide confirmatory evidence of identity, has not been observed. The pigmented Gigaspora sp. has orange to reddish-brown azygospores 275-420 pm diam with a bulbous attachment 54-74 x 67--97 )tm wide (Fig. 5). The walls are 9'6-15 pm thick and appear Trans. Br. mycol , Soc. 80 (3) (1983)
double, with the outer surface covered with small, irregular projections (Fig. 5 a, b). Whorled clusters of vesicles with irregular warty outlines were found in field material and similar structures were formed on germination hyphae with infections on Medicago sativa (Fig. 6a, b). This species corresponds very closely to Gigaspora gregaria Schenck & Nicolson (Nicolson & Schenck, 1979). The wart y outgrowths
Printed in Great Britain
Notes and brief articles are conspicuous but in some cases the projections became branched (F ig. 6b), whereas the original description of G. gregaria refers to projections on the accessory vesicle stage which ' do not become branched or coralloid' (Nicolson & Schenck, 1979). In common with certain species of this genus the germ tubes arise from preformed chambers laid down in the vicinity of the bulbous attachment (F ig. sa ). Sporocarps of Sclerocystis of two different types were recovered, but not in sufficient numbers for species ident ification . No propagules of the azygosporic genus Acaulospora were recorded in the dune sands. While there were no great differences in estimates of root infection in the three sites (T able 1), there were marked differences in the spore populations. All the endophyte species and greater spore numbers were present in the Migliarino site, but low spore numbers, of only 2 and 3 species, were found at Follonica and Alberese respectively. Ecological disturbance can affect the development of VAM (Reeves et al., 1979), and this may apply in the case of these dunes. Migliarino is a well-fixed and stable dune system not subject to excessive human activity, whereas at the other two sites, particularly Follonica, the dunes have become considerably eroded by anthropogenic factors. The stable Migliarino dunes, with a var ied endophyte flora would more closely resemble those examined in Australia (Koske, 1975) and Rhode Island, USA (Koske & Halvorson, 1981 ), than that reported from Scotland (Nicolson & Johnston, 1979). In the last apparently only one endophyte species (G. fasciculatum) was present in the pioneer colonization phase . This work confirms previous observations that VAM is a well-developed feature of sand dunes. Since these associations can affect nutrient uptake and ameliorate sand aggregation (N icolson & Johnston , 1979) and further improve water relations (H ardie & Ley ton, 1981) they may be of considerable ecological significance in such harsh environments. The authors are grateful to Dr C. Walker for helpful discussions on endophyte taxonomy.
REFERENCES
ARRIGONI, P. V. (1981). Aspetti del paesaggio vegetale che scompaiono in Italia : 1aflora e la vegetazione dei litorali sabbiosi. Atti del Seminario sui tema 'Pro-blem i scientifici e tecnici della conservaz ione del patrimonia uegetale", F irenze 18-19 Dicembre 1979, Pavia 1981, 51-57· BONFANTE-FASOLO, P ., DEXHIEMER, J. , GIANINAZZI, S.,
Trans. Br. mycol. S oc. 80 (3) (1983)
555
GIANINAZZI-PEARSON, G. & SCANNERINI, S. (1981). Cytochemical modifications in the host-fungus interface during intracellular interactions in vesicular-arbuscular mycorrhiza, Plant Science Letters ZZ, 13-21. EL-GIAHMI, A. A., NICOLSON, T. H . & DAFT, M . J. (1976). Endomycorrhizal fungi from Libyan soils. Transactions of the Br itish Mycological Society 67, 164- 169. FORSTER, S. M. (1979). Microbial aggregation of sand in an embryo dune system . Soil Biology and Bio chemistry 11, 537-543 . FORSTER, S. M . & NICOLSON, T. H. (1981). Microbial aggregation of sand in a maritime dune succession . Soil Biology and Biochemistry 13, 205-208. GERDEMANN, J. W. (1968). Vesicular-arbuscular mycorrhizas and plant growth. Annual Review of M icrobiology 6,397-4 18. GERDEMANN, J . W . & NICOLSON, T. H. (1963). Spores of mycorrhizal Endogone species extracted from soil by wet sieving and decanting. Transactions of the British Mycological Society 46, 235-244. GERDEMANN, J. W. & TRAPPE, J. M. (1974). The Endogonaceae in the Pacific North West. Mycologia Memoir no . 5. GIOVANNETTI, M. & MOSSE, B. (1980). An evaluation of techniques for measuring vesicular-arbuscular mycorrhizal infection in roots . New Phytologist 84, 489-500. HARDIE, K. & LEYTON, L. (1981). The influence of vesicular-arbuscular mycorrhiza on growth and water relations of red clover. I. In phosphate deficient soil. N ew Phytologist 89, 599-6<>8. HIRREL, M . C. , MEHRAVARAN, H . & GERDEMANN, J. W. (1978). Vesicular-arbuscular mycorrhizae in the Chenopodiaceae and Cruciferae: do they occur? Canadian Journal of Botany 56, 2813-2817. KOSKE, R. E . (1975). Endogone spores in Australian sand dunes. Canadian Journal of Botany 53, 66!Hl72. KOSKE, R. E . & HALVORSON, W. L. (1981). Ecological studies of vesicular-arbuscular mycorrhizae in a barrier sand dune. Canadian J ournal of Botany 59,1413-1422. KOSKE, R. E., SUTTON, J . C. & SHEPPARD, B. R. (1975). Ecology of Endogone in Lake Huron san d dunes. Canadian Journal of Botany 53, 87--93. MOSSE, B. & BOWEN, G . D. (1968). The distribution of Endogone spores in some Australian and New Zealand soils, and in an experimental field soil at Rothamsted. Transactions of the British Mycological S ociety 51, 485-492 . NICOLSON, T . H. & JOHNSTON, C. (1979). Mycorrhiza in the Gramineae. III. Glomus fasciculatus as the endophyte of pioneer grasses in a maritime sand dune. Transactions of the British Mycological Society 7z, 261-268. NICOLSON, T . H. & SCHENCK, N. C. (1979). Endogonaceous mycorrhiza endophytes in Florida . Mycologia 71, 178-198. PEVRONEL, N . (1923- 24). Prime ricerche sulla micorize endotrofiche e sulla microflora radicola normale delle fanerogame. Riuista di Biologia 5, 463-485 ; 6, 17-53. PEvRONEL, B. (1937). Le ' E ndogone ' quali produtti di microize endotrofiche nella fanerogame alpestre. N uovo giornale botanico iraliano 46, 584-586. PHILLIPS, J. M. & HAYMAN, D . S. (1970). Improved
Printed in Great Britain
556
Notes and brief articles
6 (a)
Trans. Br. mycol. Soc. 80 (3) (1983)
Printed in Great Britain
Notes and brief articles procedures for clearing roots and staining parasitic and vesicular-arbuscular mycorrhizal fungi for rapid assessment of infection. Transactions of the British Mycological Society 55, 158-161. REEVES, F. B., WAGNER, D., MOORMAN, T . & KIEL, J. (1979). The role of endomycorrhizae in revegetation practices in the semi-arid west. I. A comparison of incidence of mycorrhizae in severely disturbed us. natural environments. AmericanJournal of Botany 66,
557
SCANNERINI, S. & BONFANTE-FASOLO, P. (1979). Ultrastructural cytochemical demonstration of polysaccharides and proteins within the host-arcuscule interfacial matrix in an endomycorrhiza. New Phytologist 83, 87-94· SUTTON, J. c. & SHEPPARD, B. R. (1976). Aggregation of sand-dune soil by endomycorrhizal fungi. Canadian Journal of Botany 54, 326-333·
6- 13.
ARE MYCORRHIZAS ABSENT FROM THE ANTARCTIC? BY PETER CHRISTIE*
British Antarctic Survey, Natural Environment Research Council, Madingley Road, Cambridge CB3 oET AND T. H. NICOLSON
Department of Biological Sciences, University of Dundee, Dundee DDr 4HN
Vesicular-arbuscular (VA) mycorrhizas are probably the most widespread and ecologically important root infections of plants (Nicolson, 1967; Gerdemann, 1975). They have been reported from all continents except Antarctica (T in ker, 1975). Two angiosperms, Deschampsia antarctica Desv. and Colobanthus quitensis (Kunth) Bartl., have distributions extending to the maritime Antarctic (sensu Holdgate, 1964). Root samples of both these species were obtained from various antarctic sites, from the subantarctic island of South Georgia and from the Falkland Islands (T able 1). Each sample was obtained by inserting a knife into the ground and removing a portion of root system with adhering soil. Roots were washed free of soil with tap water and preserved in formalin: acetic acid: alcohol. Preserved root systems were cut into bundles, cleared in hot 10 % (w/v) KOH and stained with 0·05 % (wIv) trypan blue in lactophenol (Phillips & Hayman, 1970). Root segments which appeared to have taken up the stain were examined microscopically. In addition, root samples from sixteen of the eighteen native angiosperm species from South Georgia were examined; randomly-selected stained 1-2 cm root segments of the mycorrhizal species were observed at x 125, and the percentage of the length of each ... Present address: Agricultural and Food Chemistry Department, The Queen's University of Belfast, Newforge Lane, Belfast BT9 5PX.
segment infected was recorded. The occurrence of fine endophyte, and of dark septate mycelium on the root surface, was noted. Root/soil samples of fifteen South Georgia angiosperm species collected in 1980 were frozen, transported to the UK and wet-sieved (Gerdemann & Nicolson, 1963) for spores of Endogonaceae. The three D. antarctica and two C. quitensis root samples from South Georgia and the one D. antarctica sample collected from the Falkland Islands showed VA mycorrhizal infection but none was observed in any of the 137 root samples of these two angiosperms collected from the maritime Antarctic, including 127 samples collected in the South Orkney Islands (T able 1) and examined during a 3-year stay on Signy Island. Thus, two angiosperms which are mycorrhizal in the subAntarctic do not appear to form such associations in the maritime Antarctic. The D . antarctica roots from Cuverville Island and Livingstone Island, and some of the samples of both species from the South Orkney Islands, had dark septate mycelium on some root surfaces. Nine angiosperm species from South Georgia had VA mycorrhiza (Table 2) and seven of these also showed infection by a fine endophyte, Glomus tenue (Greenall) Hall (Hall, 1977). Dark septate hyphae were observed in nine angiosperms. Mycorrhizal plants from South Georgia and the Falkland Islands had a wide range of infection with significant differences between plant species. Uncinia
Fig. 5(a) Base of spore of pigmented Gigaspora sp. The dark area (arrowed) near the attachment denotes where the pre-germination compartments have been formed. (Bar = 50 pm) (b) Scanning electron micrograph showing irregular projections on the spore surface. (Bar = 1 lim) Fig. 6(a) Accessoryvesiclestage of the pigmented Gigaspora sp , on a root of Medicago sativa. (b) (Inset) shows that some of the projections become branched. (Bars = 20 p,m) Trans. Br. mycol. Soc. 80 (3) (1983)
Printed in Great Britain
Notes and brief articles
DENNIS, R . W . G . (1961). Some inoperculate discomycetes from New Zealand. Kew Bulletin 1S, 293-320 . KOHN, L. M . & KORF, R. P. (1975). Variation in ascomycete iodine reactions : KOH pretreatment explored. My cotaxon 3, 165-172. KORF, R . P. (1973). Discomycetes and Tuberales, In The Fungi, vol. IVA (ed. G. C. Ainsworth, F. K. Sparrow &
A. S. Sussman), pp. 249-319. New York and London: Academic Press . RAITVIIR, A. (1970). Sy nopsis of the Hyaloscypha ceae. Tartu : Academ y of Scien ces of the Estonian S.S.R . SEAVER, F . J. (1951). The North AmerIcan Cup-Fungi iinoperculates), New York.
VESICULAR-ARBUSCULAR MYCORRHIZAS IN ITALIAN SAND DUNES BY MANUELA GIOVANNETTI
Centro di Studio per la Microbiologia del Suolo, C.N.R., Via Borghetto 80, 56100 Pisa, Italy AND T. H. NICOLSON
Department of Biological Sciences, University of Dundee, Dundee DD1 4HN, Scotland
Ecological and taxonomic studies on vesiculararbuscular mycorrhizas (VAM) were initiated in Italy with the pioneer work of Peyronel (1923-24, 1937). He recorded this form of mycorrhiza in a wide variety of plants from different habitats and communities, and presented the first evidence that the endophytes belonged to the Endogonaceae. Subsequently, extensive ultrastructural studies on VAM have been carried out (Scannerini & Bonfante-Fasolo, 1979; Bonfante-Fasolo et al., 1981) but there has been little work on the ecological and taxonomic aspects of Italian endomycorrhizas. There is now considerable interest in mycorrhizas of sand-dune communities (N icolson & Johnston, 1979; Koske & Halvorson, 1981 ) and this paper records VAM in dune plants in Tuscany on the west coast of Italy. Five replicate samples of roots and rhizosphere were collected in 1980 from each of 18 angiosperms from localities near Follonica (approx. 42° 55 ' N), Migliarino and Alberese (100 km Nand 40 km S of Follonica respectively). The vegetation sucession varied considerably on these three dunes. At Migliarino there was a stable dune system, some 200 m wide, with an extensive and varied flora (Arrigoni, 1981). At the other more southerly sites the dunes were short and eroded with a paucity of higher plants. Only three species, including the dune grass Ammophila arenaria were present in all 3 sites, although a number of others were common to two sites (Table 1). Staining of the root samples (to g fresh weight for each species) was by the technique of Phillips & Hayman ( 1970) and quantitative assessment was by the grid-line intersect method (Giovannetti & Mosse, 1980) to obtain per cent root infection. Endogonaceous spores and sporocarps were extracted from 100 g samples of sand by wet-sieving and decanting (Gerdemann & Nicolson, 1963 ) down to Tram . Br . mycol . Soc. 80 (3) (1983)
a mesh size of 45 um . Of the 18 species examined from the 3 sites VAM was found in all except Cakile maritima and Convolvulus soldanella (Table 1). Mean percentage infection varied greatly with site and species . Over 60 % infection occurred in only a few plants, but species of the cosmopolitan families Gramineae, Papilionaceae and Compositae were heavily infected. The morphological appearance of the infections was highly variable with regard to the presence of arbuscules and vesicles . No doubt such differences were related to the host / endophyte combination and influenced by seasonal and edaphic factors. It was not surprising to find no infection in Cakile maritima as it is in a family generally considered to be non-mycorrhizal (Gerdemann, 1968). However, VAM did occur in two Silene spp. (Caryophyllales, Centrospermae) which are likewise reputed to be non-mycorrhizal. Mycorrhizal absences in these specific groups may not always be the rule (H irrel, Mehravaran & Gerdemann, 1978). Large amounts of rhizosphere mycelium were frequently present particularly on roots of Ammophila arenaria, Eryngium maritimum and Helichrysum stoechas. This was typically endogonaceous, showing characteristic angular projections. It frequently entangled sand grains and fragments of organic debris and attached them to root surfaces. Clearly, this mycelium was an important factor in sand aggregation as has been found for other dune systems (Forster, 1979; Forster & Nicolson, 1981; Koske , Sutton & Sheppard, 1975 ; Sutton & Sheppard, 1976). Also abundant on the roots and in sand was mycelium of a brown septate nature, which may belong to the fungus Phialophora radicicola var. graminicola (N icolson & Johnston, 1979).
The variation in appearance of infections indicated that a number of endophyte species were
Primed in Great Britain
Notes and brief articles T able
1.
553
M ean percentage root infec tion (and range) of V AM in thr ee sand dunes in Tu scany
Plant species
M igliarin o
Follonica
Alberese
Ammophila arenaria (L. ) Link (Grarnineae) L agurus ovatus L. (G rarnineae) V ulpia ligustica (All.) L ink (Grarnineae) Medicago marina L. (Leguminosae) M . littoralis Rohde ex Loisel. (L eguminosae) On onis oariegata L. (L egumin osae) Anacyclus radiatus Lo isel. (Compositae) Anthemis maritima L. (Compositae) H elichrysum litoreum Gu ss. (Compositae) H . stoechas (L.) Moen ch (Compositae) S ilene colorata Poiret (Cary ophyllaceae) S. otites (L. ) Wibel (Caryophyllaceae) Cak ile maritima Scop . (Cruciferae) Convolv ulus soldan ella L. (Convolvulaceae) Eryngium maritimum L. (Umbelliferae) Euphorbia paralias L. (Euphorbiaceae) Pancratium maritimum L. (Amaryllidaceae) Rosmarinus officinali s L. (Labiatae)
18 (10-70)
24 (20-30) 7 (5- 20) 12 (0-20)
24 (0-40)
pr esent , and this was confirmed when spore populations were examined. The numbers of spores also varied greatly with the highest being on the roots of H elichrysum stoechas. H owever, numbers of spores did not appear to be related to amounts of infection . For instance, Vulp ia ligustica from the Albere se site showed 62 % root infection, but no spores were recovered. Identification and classification of endophytes (after Gerdemann & Trappe, 1974 ) has been almost entirely from field material and more positive identifications must await the successful establishment of pot cultures. Chlamydospores and sporocarps of 4 Glomus spp. and 2 Sclerocystis spp . were observed, but only two of the Glomus spp . were positively identified : ( 1) Glomus mosseae (N ieol. & Ger d.) Gerdemann & Trappe. This species was mostl y recovered as ectocarpic chlamydospores which showed a dist inctive long funnel-shaped attachment (Fig. 1). This is similar to a form of G. mosseae which has been reported from Libya (El-Giahmi, Ni colson & Daft, 1976 ), from Australia (Mosse & Bowen, 1968) and the Pacific northwest of U.S .A. (Gerdemann & Trappe, 1974). The constancy of appearance and its occurrence here and in other parts of the world may mean that this form merits a new taxonomic status. (2) Glomus [asciculatum (T haxter sensu Gerdemann) Gerdemann & Trappe. This, one of the commonest and most variable ofendophyte species, was pre sent in the form of loose sporo carpic clusters up to 3 rom diam (Fi g. 2) varying in colour from light to dark brown. The individual chlamydospores were 20--90 pm diam when globose but irregular-shaped spore s had dimens ions of up to Trans. Br. my col. S oc. 80 (3) (1983)
62 (40-80)
12 (10-20) 72 (60-90) 10 (0-20) 28 (10-40) 48 (30-70)
40 (30-50) 26 (10-50)
36 (30-60) 2 (o-to) 16 (5- 20)
° ° 34 (20-50)
0 0
38 (30-50)
0 68 44 72 2
°
(60-80) (40-50) (6<>-90) (o-to)
Distinctly different from the above was another type of sporocarp 1-2 rom diam conta ining more than 50 chlamydospores which were 70-100 pm , hyaline to light yellow. These spores possessed a very distinct wall of two layers, both 4-5 pm th ick, the outer being hyaline and the inner yellow (F ig. 3). This fungus could also be classed as G. [as ciculatum as presently constituted (Gerdemann & Trappe, 1974 ). Pot cultures will be necessary to indicate whether it might be a different species. A further Glomus sp. has sporocarps 250-400 pm diam containing 8-24 brown spores with dimen sions 30-60 pm and single wall 5 pm th ick. This fungus was only present at the Miglia rino site where it reached up to 95 spores 100 g-1 in H . stoechas samples . It could be considered as a non-peridial form of G. microcarpum. These observations emphasize the difficulties, stressed by Gerdemann & Trappe (1974), of dealing with the G. microcarpum-fasciculatummacrocarpum complex where the criterion for species separation is mainly the size of the chlamydospores. Two species of the azygosporic genus G igaspora were widely distributed in the dune samples , one being hyaline and th e other pigmented. The former is Gigaspora calospora (N icol. & Gerd.) Gerdemann & Trappe with subglobose azygospores 182-260 pm in size. The wall is 5 pm thick with a smooth out er surface. The spore and its suspensorlike bulbous attachment (Fig. 4) are the same white-cream colour , this being a characteristic feature of G. calospora (Gerdemann & Trappe, 1974). Att empts at pot culturing this species with
108 pm.
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Notes and brief articles
554
2
3 Fig.
1.
Glomus mosseae. Note the funnel-shaped attachment. (Bar =
Fig. 2 . Sporocarps of Glomus [asciculatum. (Bar
100
pm )
= 50/tm )
Fig. 3. Chlamydospores from a sporocarp of a Glomus sp ., showing the two-layered wall. (Bar =
10 flm )
Fig. 4. Gigaspora calospora . Note that the azygospore and its attachment are concolourous. (Bar = 50 pm)
Medicago sativa have not yet been successful so the
singly-formed accessory vesicle stage, which would provide confirmatory evidence of identity, has not been observed. The pigmented Gigaspora sp. has orange to reddish-brown azygospores 275-420 pm diam with a bulbous attachment 54-74 x 67--97 )tm wide (Fig. 5). The walls are 9'6-15 pm thick and appear Trans. Br. mycol , Soc. 80 (3) (1983)
double, with the outer surface covered with small, irregular projections (Fig. 5 a, b). Whorled clusters of vesicles with irregular warty outlines were found in field material and similar structures were formed on germination hyphae with infections on Medicago sativa (Fig. 6a, b). This species corresponds very closely to Gigaspora gregaria Schenck & Nicolson (Nicolson & Schenck, 1979). The wart y outgrowths
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Notes and brief articles are conspicuous but in some cases the projections became branched (F ig. 6b), whereas the original description of G. gregaria refers to projections on the accessory vesicle stage which ' do not become branched or coralloid' (Nicolson & Schenck, 1979). In common with certain species of this genus the germ tubes arise from preformed chambers laid down in the vicinity of the bulbous attachment (F ig. sa ). Sporocarps of Sclerocystis of two different types were recovered, but not in sufficient numbers for species ident ification . No propagules of the azygosporic genus Acaulospora were recorded in the dune sands. While there were no great differences in estimates of root infection in the three sites (T able 1), there were marked differences in the spore populations. All the endophyte species and greater spore numbers were present in the Migliarino site, but low spore numbers, of only 2 and 3 species, were found at Follonica and Alberese respectively. Ecological disturbance can affect the development of VAM (Reeves et al., 1979), and this may apply in the case of these dunes. Migliarino is a well-fixed and stable dune system not subject to excessive human activity, whereas at the other two sites, particularly Follonica, the dunes have become considerably eroded by anthropogenic factors. The stable Migliarino dunes, with a var ied endophyte flora would more closely resemble those examined in Australia (Koske, 1975) and Rhode Island, USA (Koske & Halvorson, 1981 ), than that reported from Scotland (Nicolson & Johnston, 1979). In the last apparently only one endophyte species (G. fasciculatum) was present in the pioneer colonization phase . This work confirms previous observations that VAM is a well-developed feature of sand dunes. Since these associations can affect nutrient uptake and ameliorate sand aggregation (N icolson & Johnston , 1979) and further improve water relations (H ardie & Ley ton, 1981) they may be of considerable ecological significance in such harsh environments. The authors are grateful to Dr C. Walker for helpful discussions on endophyte taxonomy.
REFERENCES
ARRIGONI, P. V. (1981). Aspetti del paesaggio vegetale che scompaiono in Italia : 1aflora e la vegetazione dei litorali sabbiosi. Atti del Seminario sui tema 'Pro-blem i scientifici e tecnici della conservaz ione del patrimonia uegetale", F irenze 18-19 Dicembre 1979, Pavia 1981, 51-57· BONFANTE-FASOLO, P ., DEXHIEMER, J. , GIANINAZZI, S.,
Trans. Br. mycol. S oc. 80 (3) (1983)
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GIANINAZZI-PEARSON, G. & SCANNERINI, S. (1981). Cytochemical modifications in the host-fungus interface during intracellular interactions in vesicular-arbuscular mycorrhiza, Plant Science Letters ZZ, 13-21. EL-GIAHMI, A. A., NICOLSON, T. H . & DAFT, M . J. (1976). Endomycorrhizal fungi from Libyan soils. Transactions of the Br itish Mycological Society 67, 164- 169. FORSTER, S. M. (1979). Microbial aggregation of sand in an embryo dune system . Soil Biology and Bio chemistry 11, 537-543 . FORSTER, S. M . & NICOLSON, T. H. (1981). Microbial aggregation of sand in a maritime dune succession . Soil Biology and Biochemistry 13, 205-208. GERDEMANN, J. W. (1968). Vesicular-arbuscular mycorrhizas and plant growth. Annual Review of M icrobiology 6,397-4 18. GERDEMANN, J . W . & NICOLSON, T. H. (1963). Spores of mycorrhizal Endogone species extracted from soil by wet sieving and decanting. Transactions of the British Mycological Society 46, 235-244. GERDEMANN, J. W. & TRAPPE, J. M. (1974). The Endogonaceae in the Pacific North West. Mycologia Memoir no . 5. GIOVANNETTI, M. & MOSSE, B. (1980). An evaluation of techniques for measuring vesicular-arbuscular mycorrhizal infection in roots . New Phytologist 84, 489-500. HARDIE, K. & LEYTON, L. (1981). The influence of vesicular-arbuscular mycorrhiza on growth and water relations of red clover. I. In phosphate deficient soil. N ew Phytologist 89, 599-6<>8. HIRREL, M . C. , MEHRAVARAN, H . & GERDEMANN, J. W. (1978). Vesicular-arbuscular mycorrhizae in the Chenopodiaceae and Cruciferae: do they occur? Canadian Journal of Botany 56, 2813-2817. KOSKE, R. E . (1975). Endogone spores in Australian sand dunes. Canadian Journal of Botany 53, 66!Hl72. KOSKE, R. E . & HALVORSON, W. L. (1981). Ecological studies of vesicular-arbuscular mycorrhizae in a barrier sand dune. Canadian J ournal of Botany 59,1413-1422. KOSKE, R. E., SUTTON, J . C. & SHEPPARD, B. R. (1975). Ecology of Endogone in Lake Huron san d dunes. Canadian Journal of Botany 53, 87--93. MOSSE, B. & BOWEN, G . D. (1968). The distribution of Endogone spores in some Australian and New Zealand soils, and in an experimental field soil at Rothamsted. Transactions of the British Mycological S ociety 51, 485-492 . NICOLSON, T . H. & JOHNSTON, C. (1979). Mycorrhiza in the Gramineae. III. Glomus fasciculatus as the endophyte of pioneer grasses in a maritime sand dune. Transactions of the British Mycological Society 7z, 261-268. NICOLSON, T . H. & SCHENCK, N. C. (1979). Endogonaceous mycorrhiza endophytes in Florida . Mycologia 71, 178-198. PEVRONEL, N . (1923- 24). Prime ricerche sulla micorize endotrofiche e sulla microflora radicola normale delle fanerogame. Riuista di Biologia 5, 463-485 ; 6, 17-53. PEvRONEL, B. (1937). Le ' E ndogone ' quali produtti di microize endotrofiche nella fanerogame alpestre. N uovo giornale botanico iraliano 46, 584-586. PHILLIPS, J. M. & HAYMAN, D . S. (1970). Improved
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Notes and brief articles
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Trans. Br. mycol. Soc. 80 (3) (1983)
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Notes and brief articles procedures for clearing roots and staining parasitic and vesicular-arbuscular mycorrhizal fungi for rapid assessment of infection. Transactions of the British Mycological Society 55, 158-161. REEVES, F. B., WAGNER, D., MOORMAN, T . & KIEL, J. (1979). The role of endomycorrhizae in revegetation practices in the semi-arid west. I. A comparison of incidence of mycorrhizae in severely disturbed us. natural environments. AmericanJournal of Botany 66,
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SCANNERINI, S. & BONFANTE-FASOLO, P. (1979). Ultrastructural cytochemical demonstration of polysaccharides and proteins within the host-arcuscule interfacial matrix in an endomycorrhiza. New Phytologist 83, 87-94· SUTTON, J. c. & SHEPPARD, B. R. (1976). Aggregation of sand-dune soil by endomycorrhizal fungi. Canadian Journal of Botany 54, 326-333·
6- 13.
ARE MYCORRHIZAS ABSENT FROM THE ANTARCTIC? BY PETER CHRISTIE*
British Antarctic Survey, Natural Environment Research Council, Madingley Road, Cambridge CB3 oET AND T. H. NICOLSON
Department of Biological Sciences, University of Dundee, Dundee DDr 4HN
Vesicular-arbuscular (VA) mycorrhizas are probably the most widespread and ecologically important root infections of plants (Nicolson, 1967; Gerdemann, 1975). They have been reported from all continents except Antarctica (T in ker, 1975). Two angiosperms, Deschampsia antarctica Desv. and Colobanthus quitensis (Kunth) Bartl., have distributions extending to the maritime Antarctic (sensu Holdgate, 1964). Root samples of both these species were obtained from various antarctic sites, from the subantarctic island of South Georgia and from the Falkland Islands (T able 1). Each sample was obtained by inserting a knife into the ground and removing a portion of root system with adhering soil. Roots were washed free of soil with tap water and preserved in formalin: acetic acid: alcohol. Preserved root systems were cut into bundles, cleared in hot 10 % (w/v) KOH and stained with 0·05 % (wIv) trypan blue in lactophenol (Phillips & Hayman, 1970). Root segments which appeared to have taken up the stain were examined microscopically. In addition, root samples from sixteen of the eighteen native angiosperm species from South Georgia were examined; randomly-selected stained 1-2 cm root segments of the mycorrhizal species were observed at x 125, and the percentage of the length of each ... Present address: Agricultural and Food Chemistry Department, The Queen's University of Belfast, Newforge Lane, Belfast BT9 5PX.
segment infected was recorded. The occurrence of fine endophyte, and of dark septate mycelium on the root surface, was noted. Root/soil samples of fifteen South Georgia angiosperm species collected in 1980 were frozen, transported to the UK and wet-sieved (Gerdemann & Nicolson, 1963) for spores of Endogonaceae. The three D. antarctica and two C. quitensis root samples from South Georgia and the one D. antarctica sample collected from the Falkland Islands showed VA mycorrhizal infection but none was observed in any of the 137 root samples of these two angiosperms collected from the maritime Antarctic, including 127 samples collected in the South Orkney Islands (T able 1) and examined during a 3-year stay on Signy Island. Thus, two angiosperms which are mycorrhizal in the subAntarctic do not appear to form such associations in the maritime Antarctic. The D . antarctica roots from Cuverville Island and Livingstone Island, and some of the samples of both species from the South Orkney Islands, had dark septate mycelium on some root surfaces. Nine angiosperm species from South Georgia had VA mycorrhiza (Table 2) and seven of these also showed infection by a fine endophyte, Glomus tenue (Greenall) Hall (Hall, 1977). Dark septate hyphae were observed in nine angiosperms. Mycorrhizal plants from South Georgia and the Falkland Islands had a wide range of infection with significant differences between plant species. Uncinia
Fig. 5(a) Base of spore of pigmented Gigaspora sp. The dark area (arrowed) near the attachment denotes where the pre-germination compartments have been formed. (Bar = 50 pm) (b) Scanning electron micrograph showing irregular projections on the spore surface. (Bar = 1 lim) Fig. 6(a) Accessoryvesiclestage of the pigmented Gigaspora sp , on a root of Medicago sativa. (b) (Inset) shows that some of the projections become branched. (Bars = 20 p,m) Trans. Br. mycol. Soc. 80 (3) (1983)
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