© 2005 Heron Publishing—Victoria, Canada
Light sources with different spectra affect root and mycorrhiza formation in Scots pine in vitro
Karoliina Niemi (1, 2, 3), Riita Julkunen-Tiitto (4), Riitta Tegelberg (4) and Hely Häggman (2, 5)
1. Department of Applied Biology, University of Helsinki, P.O. Box 27, FIN-00014 University of Helsinki, Finland / 2. Finnish Forest Research Institute, Punkaharju Research Station, FIN-58450 Punkaharju, Finland / 3. Corresponding author (karoliina.niemi@helsinki.fi) / 4. Department of Biology, University of Joensuu, P.O. Box 111, FIN-80101 Joensuu / 5. Department of Biology, University of Oulu, P.O. Box 3000, FIN-90014 University of Oulu, Finland / Received March 18, 2004; accepted June 4, 2004; published online November 1, 2004
Summary
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.
Keywords:
adventitious rooting, cool white light, daylight, Pinus sylvestris, Pisolithus tinctorius, warm white light.
