GROWTH OF HETEROSIGMA CARTERAE (RAPHIDOPHYCEAE) ON NITRATE AND AMMONIUM AT THREE PHOTON FLUX DENSITIES: EVIDENCE FOR N STRESS IN NITRATE-GROWING CELLS
Article first published online: 28 JUN 2008
Journal of Phycology
Volume 31, Issue 6, pages 859–867, December 1995
How to Cite
Wood, G. J. and Flynn, K. J. (1995), GROWTH OF HETEROSIGMA CARTERAE (RAPHIDOPHYCEAE) ON NITRATE AND AMMONIUM AT THREE PHOTON FLUX DENSITIES: EVIDENCE FOR N STRESS IN NITRATE-GROWING CELLS. Journal of Phycology, 31: 859–867. doi: 10.1111/j.0022-3646.1995.00859.x
- Issue published online: 28 JUN 2008
- Article first published online: 28 JUN 2008
- Received 9 March 1995. Accepted 24 July 1995.
- cell quota;
- Heterosigma akashiwo;
- Heterosigma carterae;
- intracellular amino acids;
- photon flux density;
The marine alga Heterosigma carterae Hulburt (Raphidophyta) was grown in N-limiting batch cultures using either nitrate or ammonium as the N source, at photon flux densities (PFDs) of 50, 200, and 350 μmol·m-2·s-1 in a 12:12 h LD cycle. Carbon content could be estimated from biovolume (μg C = 0.278 × nL; R =0.98) but not reliably from pigment content. During exponential growth, ammonium-grown cells (in comparison with nitrate-grown cells at the same PFD) attained higher growth rates by at least 20%, contained more N, and had a lower C:N ratio, higher concentrations of intracellular free amino acids, and higher ratios of glutamine: glutamate (Gln: Glu) and asparagine: aspartate (Asn:Asp). Growth was nearly light-saturated on ammonium at 200 μmol·m-2·s-1 (cell-specific growth rate of 1.2 d-1) but probably not saturated in nitrate-grown cells at 350 μmol·m-2·s-1. PFD did not affect Gln: Glu or Asn: Asp for a given N source. These results indicate that the nitrate-growing cells were more N-stressed than those using ammonium (which in contrast were relatively C-stressed) and that this organism would show an enhanced competitive advantage against other species when supplied with a transient supply of ammonium rather than nitrate.