Nitrate and Ammonium Induced Photosynthetic Suppression in N-Limited Selenastrum minutum1: II. Effects of NO3− and NH4+ Addition to CO2 Efflux in the Light
AUTOR(ES)
Birch, Douglas G.
RESUMO
The effects of nitrate and ammonium addition on net and gross photosynthesis, CO2 efflux and the dissolved inorganic carbon compensation point of nitrogen-limited Selenastrum minutum Naeg. Collins (Chlorophyta) were studied. Cultures pulsed with nitrate or ammonium exhibited a marked decrease in both net and gross photosynthetic carbon fixation. During this period of suppression the specific activity of exogenous dissolved inorganic carbon decreased rapidly in comparison to control cells indicating an increase in the rate of CO2 efflux in the light. The nitrate and ammmonium induced rates of CO2 efflux were 31.0 and 33.8 micromoles CO2 per milligram chlorophyll per hour, respectively, and represented 49 and 48% of the rate of gross photosynthesis. Nitrate addition to cells at dissolved inorganic carbon compensation point caused an increase in compensation point while ammonium had no effect. In the presence of the tricarboxylic acid cycle inhibitor fluoroacetate, the nitrate-induced change in compensation point was greatly reduced suggesting the source of this CO2 was the tricarboxylic acid cycle. These results are consistent with the mechanism of N-induced photosynthetic suppression outlined by Elrifi and Turpin (1986 Plant Physiol 81: 273-279).
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=1056194Documentos Relacionados
- The Path of Carbon Flow during NO3−-Induced Photosynthetic Suppression in N-Limited Selenastrum minutum1
- Steady-State Chlorophyll a Fluorescence Transients during Ammonium Assimilation by the N-Limited Green Alga Selenastrum minutum1
- Mitochondrial Respiration Can Support NO3− and NO2− Reduction during Photosynthesis 1: Interactions between Photosynthesis, Respiration, and N Assimilation in the N-Limited Green Alga Selenastrum minutum
- Significance of Phosphoenolpyruvate Carboxylase during Ammonium Assimilation: Carbon Isotope Discrimination in Photosynthesis and Respiration by the N-Limited Green Alga Selenastrum minutum1
- Photosynthetic Assimilation of NO3− by Intact Cells of the Cyanobacterium Anacystis nidulans. Infulence of NO3− and NH4+ Assimilation on CO2 Fixation