Meaning Making in Secondary Science Classrooms

The effects of nitrate and ammonium addition on net and gross photosynthesis, CO(2) 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 CO(2) efflux in the light. The nitrate and ammmonium induced rates of CO(2) efflux were 31.0 and 33.8 micromoles CO(2) per milligram chlorophyll per hour, respectively, and represented…