Coupling and uncoupling between nitrate uptake and growth rate in Prorocentrum minimum (Dinophyceae) under different frequencies of pulsed nitrate supply

Abstract

In comparison with continuous nitrate supply, rate of cell division was not affected by 1 or 2d pulse treatments, but it fell drastically when a nitrogen source was added only every 3d. Delayed steady uptake rates were reached during the 1 or 2d pulse phases, reflecting a mid-term adaptation of the cell uptake process under discontinuous nutrient supply. This adaptation permitted P. minimum to maintain a steady growth rate under these regimes. During the 3d pulse treatment, the maximal uptake rate measured during each pulse experiment increased considerably, which reflected a long-term adaptation, but was not sufficient to maintain the initial growth rate. For low frequencies of nitrate supply, uptake and growth rate became largely uncoupled. -from Author