Root colonisation by AM fungi differs between gypsum specialist and non-specialist plants: Links to the gypsophile behaviour

Gypsum soils are among the most restrictive substrates for plant life, yet the mechanisms of plant adaptation to gypsum are still poorly understood. Arbuscular mycorrhizal fungi (AMF) can improve host plant nutrition and survival in stressful environments but little is known about the ubiquity and function of AMF in plants that grow in gypsum soils, both specialists and generalists. Previous studies indicate that most gypsophiles (specialists) show much higher concentration of nutrients than gypsovags (generalists), hence our hypothesis was that this would be related to increased mycorrhizal colonisation in gypsum specialists. We therefore quantified colonisation of the roots by mycorrhizal arbuscules (AC), vesicles (VC) and hyphae (HC) in six species of gypsophiles and six species of gypsovags growing in gypsum outcrops. Both groups of plants showed significant differences in AC, VC and HC but in contrast to our hypothesis, colonisation was greater in gypsovags than in gypsophiles. The extent of AMF colonisation does not seem to explain the distinctively high nutrient concentrations reported for gypsophiles. Our results indicate that increased AM colonisation could be a mechanism allowing non-specialist plants to cope with the restrictive conditions of gypsum. (C) 2011 Elsevier Ltd. All rights reserved.