SOME SHORT-TERM EFFECTS OF INCREASED CARBON DIOXIDE CONCENTRATION ON PHOTOSYNTHETIC ASSIMILATION IN LEAVES

Abstract

The photosynthetic assimilation of radioactive carbon dioxide by leaves from seven plant species was continuously measured in a closed system in which the concentration of carbon dioxide was abruptly increased from the atmospheric level to predetermined levels up to 2.0%. The rate of assimilation immediately increased, approximately proportional to concentration, but after about one minute began to decrease. The degree and duration of the decrease in rate of uptake varied with plant species and with concentration. This increased uptake of carbon dioxide influenced the distribution of carbon among the products of assimilation. At the lowest concentration (0.1%), serine, glycine, and glyceric acid contained most of the carbon assimilated during the experimental period, but at higher concentrations these were replaced by sucrose and alanine.