Nitrogen uptake and assimilation kinetics in Alexandrium minutum (Dynophyceae): effect of N-limited growth rate on nitrate and ammonium interactions - Université de Bretagne Occidentale Access content directly
Journal Articles Journal of Phycology Year : 2007

Nitrogen uptake and assimilation kinetics in Alexandrium minutum (Dynophyceae): effect of N-limited growth rate on nitrate and ammonium interactions

Abstract

Uptake and assimilation kinetics of nitrate and ammonium were investigated along with inhibition of nitrate uptake by ammonium in the harmful dinoflagellate Alexandrium minutum Halim at different nitrogen (N)-limited growth rates. Alexandrium minutum had a strong affinity for nitrate and ammonium (Ks50.26 0.03 and 0.31 0.04 lmol .L 1, respectively) whatever the degree of N deficiency of the cells. Ammonium was always the preferred form of nitrogen taken up (rNO3=rNH4 50.42-0.50). In the presence of both forms, nitrate uptake was inhibited by ammonium, and inhibition was particularly marked in N-sufficient cells (Imax~0.9 and Ki50.31-0.56 lmol .L 1). In the case of N assimilation, ammonium was also the preferred form in N-deficient cells (rassim NO3=rassim NH4 50.54-0.72), whereas in N-sufficient cells, both N sources were equally preferred (rassim NO3=rassim NH4 50.90-1.00). The comparison of uptake and assimilation rates highlighted the ability of A. minutum to significantly store in 1 h nitrate and ammonium in amounts sufficient to supply twice the daily N requirements of the slowest-growing N-deficient cells. Nitrogen uptake kinetic parameters of A. minutum and their ecological implications are discussed.

Dates and versions

hal-00633672 , version 1 (19-10-2011)

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Jean-François Maguer, Stéphane L'Helguen, Christian Madec, Claire Labry, Pierre Le Corre. Nitrogen uptake and assimilation kinetics in Alexandrium minutum (Dynophyceae): effect of N-limited growth rate on nitrate and ammonium interactions. Journal of Phycology, 2007, 43, pp.295-303. ⟨10.1111/j.1529-8817.2007.00334.x⟩. ⟨hal-00633672⟩
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