Short-Term Fixation of 14Carbon by the Submerged Aquatic Angiosperm Potamogeton pectinatus

In ¹⁴C fixation experiments, 3-phosphoglyceric acid was thefirst product of carbon assimilation in the light in Potamogetonpectinatus. The pattern of early ¹⁴C-labelled compounds wasthe same over a range of pH values of the medium from 3.5 to8.1. Rates of ¹⁴C incorporation declined with increasing pHof the medium indicating that free CO₂ is the major exogenoussource of carbon for photosynthesis in Potamogeton pectinatus.