MES [2-(N-MORPHOLINE)-ETHANE SULFONIC-ACID] BUFFER PROMOTES THE GROWTH OF EXTERNAL HYPHAE OF THE ARBUSCULAR MYCORRHIZAL FUNGUS GLOMUS INTRARADICES IN AN ALKALINE SAND

In this work we investigated the hypothesis, suggested by unpublished experiments carried out previously, that application of MES [2-(N-morp holino)-ethane sulphonic acid] buffer to the substrate of plants hosti ng the arbuscular mycorrhizal fungus Glomus intraradices might favour the growth of external hyphae. The substrate of Trifolium pratense pla nts, with or without G. intraradices inoculum, was treated twice weekl y, between weeks 5 and 11 of growth, plant with distilled water, P-sup plemented 10% Hewitt nutrient solution (H+P), 51 mM in H+P or 1 mM TRI S-HCl in H+P. MES buffer increased the length of external G. intraradi ces hyphae and the density of propagules in the substrate, but plant g rowth was not affected, Although both TRIS-HCl and MES caused substrat e pH to fall (from 8.51 to 7.35 and 7.17, respectively), only MES indu ced a significant increase in external hypha length. We conclude that the effect of MES on external hypha length was not due to plant growth or to substrate pH per se.