Experimentelle Untersuchungen zur Aufnahme und zum Stoffwechsel von Stickstoff in Wurzeln ausgewählter Bodenpflanzen aus naturnahen Ökosystemen

Abstract

Mechanisms of diversity changes in plant communities on physiological level are examined up to now only inadequately. Therefore, the objective of these pot experiments was to study differential adaptations in root uptake of inorganic N as well as in intracellular N storage of key metabolites in plants from the floor vegetation of Scots pine forests (B. sylvaticutn, A. flexuosa, C. epigejos, V. myrtillus, R. idaeus, R. fruticosus). Fertilizers of ¹⁵N labelled ¹⁵NH₄NO₃ and NH₄ ¹⁵NO₃ were applied to determine the N uptake and the accumulation of amino acids. The results show that the rates for ammonium and nitrate uptake (mg ¹⁵N g^-1 d^-1) correspond with the glutamine concentrations in the roots. The NH ⁺₄ -tolerant ericaceous shrub V. myrtillus accumulates excessively glutamine and shows the lowest uptake for both N forms. In sharp contrast, the nitrophile blackberry R. fruticosus has a low glutamine accumulation and a much higher uptake for nitrate and ammonium. In consequence, nitrophile characteristics of plants result in high N uptake and in a reduced accumulation of N in glutamine. In addition, it can be shown that in contrast to NH₄ ⁺-tolerant plants, which accumulate ammonium in glutamine and arginine, nitrophile plants prefer asparagine as amino acid for the intracellular N storage.