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BIOMASS ALLOCATION IN AN AGROPYRON SMITHII‐GLOMUS SYMBIOSIS
Author(s) -
Miller R. Michael,
Jarstfer Amiel G.,
Pillai Jan K.
Publication year - 1987
Publication title -
american journal of botany
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.218
H-Index - 151
eISSN - 1537-2197
pISSN - 0002-9122
DOI - 10.1002/j.1537-2197.1987.tb08585.x
Subject(s) - biology , tiller (botany) , fungus , biomass (ecology) , agronomy , symbiosis , phosphorus , hypha , botany , nutrient , mycorrhiza , ecology , bacteria , genetics , materials science , metallurgy
The type of response the steppe grass Agropyron smithii Rydb. exhibits to mycorrhizal fungi is dependent upon where along the resource gradient the experiment is conducted. At the lower end of a soil‐phosphorus (P) gradient (2 μg P g ‐1 soil) mycorrhizal A. smithii biomass was 35% greater than its nonmycorrhizal counterpart; while at the high end of the gradient (20 μg P g ‐1 soil) no difference in host biomass production was evident. Mycorrhizal plants were shorter in stature ( P < 0.002) and produced more tillers ( P < 0.0001) than nonmycorrhizal plants. The stature and tiller response was more pronounced at the high end of the soil‐P gradient. The partitioning of the mycorrhizal fungus was influenced by the soil‐P gradient. At the lower end of the gradient the majority of the fungus was produced extramatrically, where over 5,000 cm of hyphae per plant were encountered after 10 wk growth. While at the high end of the gradient, the majority of fungus was produced internally. The highest mycorrhizal dependency values were measured at the lower end of the soil‐P gradient where cost to the host (as measured by fungus biomass expressed as a percentage of the root system) was also highest. Increasing shoot and root‐P concentrations were correlated with decreasing external fungus biomass. A positive association between tiller production and internal fungus biomass also existed. The significance of these findings, as well as the need to consider characteristics which measure fitness of a host in evaluating the mycorrhizal association of grasses, are discussed.