Seedlings were grown in a sand: expanded clay substrate (1:1) under 16h light at 25'C and fertilized, unless otherwise noted, twice a week with half strengths Hoagland solution . For inoculation with Glomus intraradices, an inoculum was added to the substrate at 10% (v/v). G. intraradices (strain BB-E, provided by Agrauxine, Dijon, France) was used.