Mycorrhizas formed by Gigaspora calospora and Glomus fasciculatum on subterranean clover in relation to soluble carbohydrate concentrations in roots

B. D. Thomson, A. D. Robson, L. K. Abbott

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61 Citations (Scopus)

Abstract

At several times during plant growth, we compared the effects of two irradiances (plants were either not shaded or were shaded to reduce 60–70% of the photon flux in the glasshouse) and two concentrations of soil phosphorus (P) (35 and 105 μg−1 P g−1 soil) on the formation of vesicular‐arbuscular (VA) mycorrhizas on Trifolium subterraneum L. by Gigaspora calospora (Nicol. & Gerd.) Gerd. and by Glomus fasciculatum (Thaxter sensu Gerd.) Gerd. & Trappe. 

By the fifth week from sowing, the proportion of root length infected by both G. calospora and G. fasciculatum was reduced in plants grown at the greater concentration of P and in plants grown without shade. These effects were associated with decreased concentrations of soluble carbohydrates in roots at earlier harvests. Decreased concentrations of soluble carbohydrates in the roots of unshaded plants were not associated with increased concentrations of P in the plant. 

The percentage of root length infected by G. calospora was decreased to a greater extent than that of G. fasciculatum with similar reductions in the concentrations of soluble carbohydrates in roots. This effect may partly explain why the percentage of root length infected by G. calospora is more sensitive than that of G. fasciculatum to increasing P supply. G. calospora and G. fasciculatum may also differ in the extent to which P may directly affect their ability to form mycorrhizas. 

The effects of P supply and shading on the percentage of root length infected by G. calospora and by G. fasciculatum were not apparent before the fourth week from sowing. These factors may have affected the ability of the mycorrhizal fungi to spread by secondary infections.

Original languageEnglish
Pages (from-to)217-225
Number of pages9
JournalNew Phytologist
Volume114
Issue number2
DOIs
Publication statusPublished - Feb 1990

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