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Nitrogen affects the phosphorus response of VA mycorrhiza

1990; Wiley; Volume: 115; Issue: 2 Linguagem: Inglês

10.1111/j.1469-8137.1990.tb00456.x

1469-8137

David M. Sylvia, L. H. NEAL,

Plant-Microbe Interactions and Immunity

summary Root colonization by vesicular‐arbuscular (VA) mycorrhizal fungi is often suppressed by phosphorus (P) additions; however, nitrogen (N) additions have been reported to both stimulate and suppress root colonization. The objective of this research was to examine colonization of Allium cepa L. roots at a range of P and N concentrations in order to clarify the effects of these nutrients on root colonization. In the first experiment, conducted under N‐limiting conditions, P addition had no effect on root colonization by Glontus etunicatum Becker & Gerdemann and increased root colonization by Gigaspora margarita Gerdemann and Trappe. In the second experiment, conducted under N‐sufficient conditions, P addition suppressed colonization by G. etunicatum. In the third experiment, P and N additions were such that tissue P:N ratios ranged from 0–03 (P limiting) to 017 (N limiting). No relationship was found between P:N ratio and root colonization for two isolates of G. etunicatum. Root colonization was not affected by P addition when plants were deficient in N but, when N was sufficient, P addition suppressed root colonization. These results demonstrate that plant N stress affects the resistance of the host root to colonization by VA mycorrhizal fungi.