Open AccessNitrate Utilization by the Diatom Skeletonema costatum
Author(s) -
Juan L. Serra,
Marı́a J. Llama,
Eduardo Cadenas
Publication year - 1978
Publication title -
plant physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.554
H-Index - 312
eISSN - 1532-2548
pISSN - 0032-0889
DOI - 10.1104/pp.62.6.987
Subject(s) - nitrate , nitrite , chemistry , diatom , nitrogen , cycloheximide , kinetics , environmental chemistry , incubation , diffusion , saturation (graph theory) , botany , biochemistry , biology , physics , organic chemistry , mathematics , quantum mechanics , combinatorics , protein biosynthesis , thermodynamics
Nitrate uptake has been studied in nitrogen-deficient cells of the marine diatom Skeletonema costatum. When these cells are incubated in the presence of nitrate, this ion is quickly taken up from the medium, and nitrite is excreted by the cells. Nitrite is excreted following classical saturation kinetics, its rate being independent of nitrate concentration in the incubation medium for nitrate concentration values higher than 3 micromolar. Nitrate uptake shows mixed-transfer kinetics, which can be attributed to the simultaneous contributions of mediated and diffusion transfer. Cycloheximide and p-hydroxymercuribenzoate inhibit the carrier-mediated contribution to nitrate uptake, without affecting the diffusion component. When cells are preincubated with nitrate, the net nitrogen uptake is increased.