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Nitrogen uptake and translocation by Chara
Vermeer, C.P.; Escher, M.; Portielje, R.; de Klein, J.J.M. (2003). Nitrogen uptake and translocation by Chara. Aquat. Bot. 76(3): 245-258. dx.doi.org/10.1016/s0304-3770(03)00056-1
In: Aquatic Botany. Elsevier Science: Tokyo; Oxford; New York; London; Amsterdam. ISSN 0304-3770, more
Peer reviewed article  

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Keywords
    Nitrates; Nitrogen; Nitrogen fixation; Plant nutrition; Uptake; Chara Linnaeus, 1753 [WoRMS]; Netherlands, Wolderwijd L. [Marine Regions]; Fresh water

Authors  Top 
  • Vermeer, C.P.
  • Escher, M.
  • Portielje, R., correspondent
  • de Klein, J.J.M.

Abstract
    The potential for above-ground and below-ground uptake and subsequent internal translocation of ammonium (NH4+) and nitrate (NO3-) by the macroalga Chara spp. was investigated. In a two compartment experimental set-up separating above-ground and below-ground algal parts, the charophytes were exposed to various combinations of 15N-labelled NH4+ and NO3-. Uptake in one compartment and translocation to the other were measured. Chara spp. was able to take up and translocate nitrogen between below-ground and above-ground parts. Uptake of 15NH4+ in rhizoids was two-fold higher than that of 15NO3-, indicating a preferential uptake of 15NH4+. Translocation after 5 days was always less in the direction from above-ground to below-ground parts (on average 2% of total 15N uptake), than in the below-ground to above-ground direction (on average 29%). Translocation occurred when the ratio of 15N-atomic percentage in the algal material in the exposed compartment roughly exceeded 2%, and was thus more determined by the internal gradient in the 15N content than by the nature of the N source (either NH4+ or NO3-). Translocation of 15N from the below-ground to the above-ground compartment also occurred when the charophytes were exposed to high concentrations of either NO3- or NH4+ in the above-ground compartment. The results of this study are supportive for a mechanism with preferential uptake of NH4+ over NO3-, and subsequent passive diffusion between cells as the dominant transport mechanism.

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