title: Mycorrhiza symbiosis increases the surface for sunlight capture in Medicago truncatula for better photosynthetic production.
abstract: Arbuscular mycorrhizal (AM) fungi play a prominent role in plant nutrition by supplying mineral nutrients, particularly inorganic phosphate (Pi), and also constitute an important carbon sink. AM stimulates plant growth and development, but the underlying mechanisms are not well understood. In this study, Medicago truncatula plants were grown with Rhizophagus irregularis BEG141 inoculum (AM), mock inoculum (control) or with P(i) fertilization. We hypothesized that AM stimulates plant growth through either modifications of leaf anatomy or photosynthetic activity per leaf area. We investigated whether these effects are shared with P(i) fertilization, and also assessed the relationship between levels of AM colonization and these effects. We found that increased P(i) supply by either mycorrhization or fertilization led to improved shoot growth associated with increased nitrogen uptake and carbon assimilation. Both mycorrhized and P(i)-fertilized plants had more and longer branches with larger and thicker leaves than the control plants, resulting in an increased photosynthetically active area. AM-specific effects were earlier appearance of the first growth axes and increased number of chloroplasts per cell section, since they were not induced by P(i) fertilization. Photosynthetic activity per leaf area remained the same regardless of type of treatment. In conclusion, the increase in growth of mycorrhized and P(i)-fertilized Medicago truncatula plants is linked to an increase in the surface for sunlight capture, hence increasing their photosynthetic production, rather than to an increase in the photosynthetic activity per leaf area.
authors.affiliation: Department of Biological and Environmental Sciences, University of Gothenburg, Box 461, 405 30 Gothenburg, Sweden.
authors.forename: Lisa
authors.initials: L
authors.lastname: Adolfsson
authors.affiliation: Department of Plant Anatomy, Eötvös Loránd University, H-1117 Budapest, Hungary.
authors.forename: Katalin
authors.initials: K
authors.lastname: Solymosi
authors.affiliation: Department of Biological and Environmental Sciences, University of Gothenburg, Box 461, 405 30 Gothenburg, Sweden.
authors.forename: Mats X
authors.initials: MX
authors.lastname: Andersson
authors.affiliation: Department of Plant Anatomy, Eötvös Loránd University, H-1117 Budapest, Hungary.
authors.forename: Áron
authors.initials: Á
authors.lastname: Keresztes
authors.affiliation: Department of Biological and Environmental Sciences, University of Gothenburg, Box 461, 405 30 Gothenburg, Sweden.
authors.forename: Johan
authors.initials: J
authors.lastname: Uddling
authors.affiliation: Mer, Molécules, Santé, MicroMar-EA2160, LUNAM Université, IUML - FR 3473 CNRS, University of Le Mans, 72085 Le Mans Cedex 9, France.
authors.forename: Benoît
authors.initials: B
authors.lastname: Schoefs
authors.affiliation: Department of Biological and Environmental Sciences, University of Gothenburg, Box 461, 405 30 Gothenburg, Sweden.
authors.forename: Cornelia
authors.initials: C
authors.lastname: Spetea
mesh_terms: D002244:Carbon / Q000378:metabolism; D055137:Glomeromycota / Q000502:physiology*; D046913:Medicago truncatula / Q000033:anatomy & histology / Q000254:growth & development* / Q000382:microbiology*; D038821:Mycorrhizae / Q000502:physiology*; D009584:Nitrogen / Q000378:metabolism; D010788:Photosynthesis; D018515:Plant Leaves / Q000033:anatomy & histology; D013472:Sunlight; D013559:Symbiosis
chemical_list: D002244:Carbon; D009584:Nitrogen