GROWTH-RESPONSE OF 3 FESTUCA-RUBRA CLONES TO LIGHT QUALITY AND ARBUSCULAR MYCORRHIZA

The influence of the arbuscular mycorrhizal fungus - Glomus etunicatun and changes in light quality (decrease of red/far-red ratio) on the g rowth of three Festuca rubra clones, ecotypes originating from a mount ain grassland region, was studied in a growth chamber experiment. Inoc ulation with the arbuscular mycorrhizal fungus and low red/far-red rat io decreased both the number of tillers and the biomass of treated pla nts. Significant interactions between the treatments were found and mo st of the growth characteristics were reduced further when both treatm ents were applied simultaneously. Inoculation with the arbuscular myco rrhizal fungus also resulted in reduced maximum height of tillers, whe reas low red/far-red ratio caused the maximum height of tillers to inc rease. Differences in plasticity were found for the three Festuca rubr a clones. Response to one treatment was strongly modified by the other treatment. This indicates that the arbuscular mycorrhizal fungus and red/far-red ratio can differentially influence the growth of Festuca r ubra clones and thus modify their relative competitive abilities which can consequently have implications for the coexistence mechanisms wit hin plant population, thereby potentially influencing plant canopy and community structure.