Mycorrhizal symbiosis effects on growth of chalk false-brome (Brachypodium pinnatum) are dependent on the environmental light regime.
AMF (arbuscular mycorrhizal fungi) colonization of the grass chalk false-brome (Brachypodium pinnatum (L.) P. B.) was studied in selected habitats under spatially different light regimes: (a) shade condition under oak trees, (b) half shade in a shrubby area and (c) full-sun conditions on unshaded grassland. This study assessed the variations in AMF colonization of the grass dependent on the light supply in field habitats. Soil, root and shoot samples were collected four times during the vegetation period (in June, July, September and October). Root colonization, root and shoot biomass as well as soil water content were determined. The highest rate of AMF colonization was detected in June under half-sun and full-sun conditions, where about 50% of the roots were colonized. The average amount of arbuscules was less than 20% in the roots at the three sites, with the highest number of arbuscules in June, under half-sun and full-sun conditions, however, not under the trees. Overall, best mycorrhizal colonization occurred during summer, and its rate decreased in autumn. This tendency inversely correlated with the amount of precipitation, and thus with the water content of soils. The high colonization rate of the examined root samples, and also its seasonal fluctuation, might reflect the importance of the symbiosis where inorganic nutrients and water are the growth-limiting factors. The marginal AMF colonization of chalk false-brome under shade conditions indicates that plants do not use AMF under all stress conditions. When low light limits photosynthesis and thus growth of the plants, they dispense with the colonization of AMF in order to save the expenditure of organic carbon.
Institute for Soil Sciences and Agricultural Chemistry, Centre for Agricultural Research, Hungarian Academy of Sciences, Herman Ottó út 15, H-1022 Budapest, Hungary.
Anna
A
Füzy
Botanical Institute, The University of Cologne, D-50674 Koeln, Germany. Electronic address: Hermann.Bothe@uni-koeln.de.
Hermann
H
Bothe
Institute of Ecology and Botany, Centre for Ecological Research, Hungarian Academy of Sciences, Alkotmány út 2-4, H-2163 Vácrátót, Hungary.
Edit
E
Molnár
Department of Soil Sciences and Water Management, Faculty of Horticulture, Corvinus University of Budapest, Villanyi ut 29-43, H-1018 Budapest, Hungary. Electronic address: borbala.biro@uni-corvinus.hu.
Borbála
B
Biró
D018533:Biomass; D058431:Brachypodium / Q000254:growth & development / Q000382:microbiology* / Q000528:radiation effects*; D004777:Environment; D006814:Hungary; D038821:Mycorrhizae / Q000502:physiology* / Q000528:radiation effects; D010783:Photometry; D010788:Photosynthesis / Q000528:radiation effects; D018517:Plant Roots / Q000254:growth & development / Q000382:microbiology / Q000528:radiation effects; D012988:Soil Microbiology; D013054:Spectrophotometry, Atomic; D013312:Stress, Physiological / Q000528:radiation effects; D013559:Symbiosis / Q000528:radiation effects*
Arbuscular mycorrhiza; Brachypodium pinnatum; Chalk false-brome; Light stress; Stress-alleviation by mycorrhiza