title: Light sources with different spectra affect root and mycorrhiza formation in Scots pine in vitro.
abstract: We studied the effects of broad-spectrum light quality on the interaction between the ectomycorrhizal fungus Pisolithus tinctorius (Pers.) Coker and Couch and Scots pine (Pinus sylvestris L.) seedlings and hypocotyl cuttings cultured in vitro. The light sources were cool white (CW), warm white (WW) and red-rich daylight (RD) fluorescent lamps. Inoculation with P. tinctorius enhanced adventitious root formation of the cuttings in all light treatments. Rooting of the inoculated cuttings was highest in WW light (89%), followed by CW (73%) and RD light (66%). During 6 weeks of in vitro culture, rooted cuttings formed only a few lateral roots. The fungus grew over lateral roots, but the Hartig net was absent in all light treatments. In non-inoculated cuttings, neither root formation nor subsequent root growth was affected by light quality. In the seedling experiment, inoculation in the WW treatment resulted in a significantly (P < 0.05) greater number of lateral roots than inoculation in the RD treatment. The percentage of lateral roots covered with fungal hyphae was also highest in WW light (62%), followed by CW (50%) and RD (27%) light. A similar pattern was observed in the intensity of Hartig net formation. We conclude that effects of broad-spectrum light quality on the ectomycorrhizal fungus-root interaction are dependent on the developmental stage of the root.
authors.affiliation: Department of Applied Biology, University of Helsinki, P.O. Box 27, FIN-00014 University of Helsinki, Finland. karoliina.niemi@helsinki.fi
authors.forename: Karoliina
authors.initials: K
authors.lastname: Niemi
authors.forename: Riita
authors.initials: R
authors.lastname: Julkunen-Tiitto
authors.forename: Riitta
authors.initials: R
authors.lastname: Tegelberg
authors.forename: Hely
authors.initials: H
authors.lastname: Häggman
mesh_terms: D001487:Basidiomycota / Q000502:physiology; D066298:In Vitro Techniques; D008027:Light; D038821:Mycorrhizae / Q000502:physiology*; D041605:Pinus sylvestris / Q000382:microbiology* / Q000502:physiology; D018517:Plant Roots / Q000382:microbiology* / Q000502:physiology; D036226:Seedlings / Q000382:microbiology / Q000502:physiology