Aspects of nitrogen assimilation by cultures of green algae

L.H.J. Bongers

Research output: Thesisinternal PhD, WU

Abstract

The N/C relation in green algae was about 0.2, but with N starvation this ratio may decline to 0.04. Such treatment also decreased the chlorophyll content of the cells as well as the rates of photosynthesis and growth.

Supply of substrate N to N-starved algae resulted in formation of cells of 'normal' character. At pH values of 7 to 8, both NO 2- and N0 3- were assimilated at approximately the same rate.

Algae of normal N/C relation did not assimilate substrate N (NO 2 - or NO 3 -) if illuminated without a carbon source. Instead, NO 3 - and NO 2- became reduced and NH 3 was excreted into the surrounding medium.

In weak light, the rate of NH 3 excretion (i.e. reduction of NO 3 - in the absence of CO 2 ) was equivalent to the rate of CO 2 reduction (in the absence of N0 3- ); if both substrates ( NO 3- + CO 2 ) were present together both rates decreased, indicating competition for the same reduction.

In strong light (without CO 2 ) the rate of NO 3- conversion into NH 3 was a fifth of the rate of CO 2 reduction. Nitrate and carbon dioxide did not compete for the reduction in strong light.

It was concluded that nitrate reduction was not necessarily dependent upon products of photosynthesis.

Original languageEnglish
QualificationDoctor of Philosophy
Awarding Institution
  • Wageningen University
Supervisors/Advisors
  • Wassink, E.C., Promotor
Award date21 Dec 1956
Place of PublicationWageningen
Publisher
Publication statusPublished - 1956
Externally publishedYes

Keywords

  • chlorophyta
  • assimilation
  • nitrogen
  • sulfur
  • phosphorus

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