Nitrate depletion and pH changes induced by the extraradical mycelium of the arbuscular mycorrhizal fungus Glomus intraradices grown in monoxenic culture
Article first published online: 28 APR 2006
Volume 133, Issue 2, pages 273–280, June 1996
How to Cite
BAGO, B., VIERHEILIG, H., PICHÉ, Y. and AZCÓN-AGUILAR, C. (1996), Nitrate depletion and pH changes induced by the extraradical mycelium of the arbuscular mycorrhizal fungus Glomus intraradices grown in monoxenic culture. New Phytologist, 133: 273–280. doi: 10.1111/j.1469-8137.1996.tb01894.x
- Issue published online: 28 APR 2006
- Article first published online: 28 APR 2006
- (Received 14 September 1995; accepted 9 January 1996)
- Glomus intraradices;
- extraradical mycelium;
- monoxenic culture;
- nitrate depletion;
The effect of the extraradical mycelium of the arbuscular mycorrhizal (AM) fungus Glomus intraradices Smith & Schenck on nitrate uptake and on the pH of the medium was studied in a monoxenic culture with tomato (Lycopersicon esculentum Mill. var. Vendor) roots obtained from root organ culture. The symbiosis was established in compartmented Petri dishes containing agar media amended with the pH indicator bromocresol purple. A pattern of pH changes was revealed as the symbiosis progressed in the media of the Petri dish compartments containing the dual, arbuscular-mycorrhizal fungi/root, culture as well as in the media of the hyphae, root-free compartments, in which the extraradical hyphae developed extensively, coming from the compartment containing the symbiosis. The colour changes in the media were measured spectrophotometrically, whilst maintaining the monoxenic conditions. The extraradical hyphae of G. intraradices strongly increased the pH of nutrient-free medium when supplied with nitrate, whereas the pH decreased m the absence of this N source. The hyphae developing from germinated spores and growing in axenic, nitrate-amended media did not induce any increase in pH. Nitrogen analysis revealed that a depletion of nitrate in the media accompanied increased pH.
These results point towards an active uptake of nitrate by the extraradical mycelium of G. intraradices, probably coupled to a H+-symport mechanism. The pH changes induced by AM fungal hyphae and the possible influence of the establishment of a functional symbiosis on these pH changes are discussed.