Abstract
This is the first report of the mycorrhizal status of Welwitschia mirabilis, a gymnosperm endemic to the Namib Desert. Like all other gymnosperms except the Pinaceae and Gnetaceae, W. mirabilis is associated with vesicular-arbuscular mycorrhizal (VAM) fungi. Mycorrhizal colonization of roots and the diversity and abundance of VAM species were determined at seven sites. Six sites received annual rainfall of 0–100 mm, varying widely from year to year. The seventh site experienced more predictable annual rainfall of 150–200 mm. Perennial vegetation was sparse at the six low-rainfall sites. Dry annual grasses from previous rain events were present at only three of these six sites and mean mycorrhizal colonization levels of W. mirabilis at these three sites were as high as 18%. W. mirabilis was not mycorrhizal at sites where grasses were absent. The seventh site, receiving higher rainfall, supported small trees and annual grasses in addition to W. mirabilis. Mycorrhizal colonization levels of W. mirabilis at this site were significantly higher than at the other six sites, closely paralleling those of the surrounding annual grasses. The mycorrhizal flora of W. mirabilis consisted of four Glomus species. These taxa were not unique to W. mirabilis, having been found with Stipagrostis and Cladoraphis grasses throughout the Namib and Kalahari deserts.
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References
Bornman CH (1972) Welwitschia mirabilis: observations on general habitat, seed, seedling, and leaf characteristics. Madoqua 11:53–56
Bornman CH (1977) Welwitschia mirabilis: structural and functional anomalies. Madoqua 10:21–31
Daniels B, Skipper H (1982) Methods for the recovery and quantitative estimation of propagules from soil. In: Schenck N (ed) Methods and principles of mycorrhizal research. American Phytopathological Society, St Paul, Minn, pp 29–36
Eller BM, Willert DJ von, Brinckmann E, Baasch R (1983) Ecophysiological studies on Welwitschia mirabilis in the Namib Desert. S Afr J Bot 2:209–223
Fassi B (1957) Ectomycorhizie chez le Gnetum africanum Welw. due a Scleroderma sp. Bull Soc Fr Mycol 73:280–285
Foster AS, Gifford EM Jr (1959) Comparative morphology of vascular plants. Freeman, San Francisco
Giess W (1971) A preliminary vegetation map of South West Africa. Dinteria 4:1–114
Giovannetti M, Mosse B (1980) An evaluation of techniques for measuring vesicular-arbuscular mycorrhizal infection in roots. New Phytol 84:489–500
Harley JL, Smith SE (1983) Mycorrhizal symbioses. Academic Press, London New York
Herre H (1961) The age of Welwitschia bainesii (Hook.f) Carr.: C14 research. S Afr J Bot 27:139–140
Kers LE (1967) The distribution of Welwitschia mirabilis Hook.f. Sven Bot Tidskr 61:97–125
Kormanik PP, McGraw AC (1982) Quantification of vesicular-arbuscular mycorrhizae in plant roots. In: Schenck N (ed) Methods and principles of mycorrhizal research. American Phytopathological Society, St Paul, Minn, pp 37–46
Koske RE, Gemma JN (1989) A modified procedure for staining roots to detect VA mycorrhizas. Mycol Res 92:486–505
Miller RM, Moorman TB, Schmidt SK (1983) Interspecific plant association effects on vesicular-arbuscular mycorrhiza occurrence in Atriplex conferticola (Torr.& Frem.) S. Wats. New Phytol 95:241–245
Read DJ, Koucheki HK, Hodgson J (1976) Vesicular-arbuscular mycorrhiza in natural vegetation systems. I. The occurrence of infection. New Phytol 76:641–653
Robinson MD, Seely MK (1980) Physical and biotic environments of the southern Namib dune ecosystem. J Arid Environ 3:183–203
Schenck NC, Perez Y (1990) Manual for the identification of VA mycorrhizal fungi. Synergistic, Gainesville, Fla
StJohn TV (1980) A survey of mycorrhizal infection in an Amazonian rain forest. Acta Amazonica 10:527–533
Warner NJ, Allen MF, MacMahon JA (1987) Dispersal agents of vesicular-arbuscular mycorrhizal fungi in a disturbed arid ecosystem. Mycologia 79:721–730
Willis JC (1973) A dictionary of the flowering plants and ferns. Cambridge University Press, Cambridge, UK
Zar JH (1984) Biostatistical analysis. Prentice-Hall, Englewood Cliffs, NJ
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Jacobson, K.M., Jacobson, P.J. & Miller, O.K. The mycorrhizal status of Welwitschia mirabilis . Mycorrhiza 3, 13–17 (1993). https://doi.org/10.1007/BF00213462
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DOI: https://doi.org/10.1007/BF00213462