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Introduction
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Methods developped in phase 2 have been applied in different experiments of our SFB (phytotron B5, labelling experiment A6, lysimeter study B12, Kranzberg Forest B4). Additionally, methods were further developped in order to study functions in the mycorrhizosphere under different stress scenarios and at different ontogenetic scales.
In joined experiments, we studied functions connected with matter fluxes, nutrient mobilisationand pathogen defence. We analysed stable isotopes, diversity of mycorrhizal populations and enzyme activities. New enzyme assays were developed with the aim to relate activities to enzyme proteins.
Together with the modelling project C2, a concept has been developed that will allow to implement mycorrhizosphere processes into the plant model PLATHO.
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Results
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Method development: multiple enzyme profiling of ectomycorrhizae
Based on a method established and published in phase 2, we further developed the nmethod especially by enlarging the spectrum of functions that are addressed (Courty et al., 2005).
This method has already been applied in current experiments.
Enzymatic profiles of ectomycorrhizae from Kranzberg Forest
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Change of enzyme activity profiles under stress
The influence of competition and ozone on young spruce and beech was studied in a phytotron experiment conducted by project B5. Reactions in the mycorrhizosphere show both, a strong effect of competition and signifcant ozone effects on most enzyme activities. These results confirmed findings from the previous phase that showed an influece of plant stress on biochemical features of soils.
Enzyme activities in soil samples from the phytotron experiment B5 phase 3
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C-allocation in mycorrhizal roots
In the same experiment, plants were labelled with the stable carbon isotope13C applied as 13CO2. The photosynthetically fixed, heavy isotope can be traced through the plant into the soil.
B9 analysed mycorrhizal and non-mycorrhizal roots after labelling. In the case of mycorrhizae of Tomentella sp., the plant species was found to play a role in C-allocation (higher d13C-values in spruce) while ozone had no direct influence.
However, in mixed culture, beech allocated more C into the mycorrhizosphere under elevated ozone.Thsi can be interpreted as stimulated root growth and consequently as a possible shift in competitive behaviour of beech which is less competitive than spruce under ambient ozone.
d13C-values in mycorrhizae of the phytotron experiment B5 phase 3
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Current investigations
Data from other experiments are currently being evaluated. The overall perspective is a comparison on different experimental scales: ontogenetic scale from young to old trees, complexity of plant communities (single plants, small containers with 6-20 plants, natural communitites), and controlled to natural environments (greenhouse, phytotron, lysimeter, forest stand).
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