Effect of ammonia on photosynthetic carbon fixation in isolated spinach leaf cells

Abstract

Ammonia stimulated photosynthetic ¹⁴CO₂ fixation in isolated spinach cells under conditions of saturating light intensity and adequate CO₂ supply. Increasing temperature increased photosynthesis and promoted the stimulation of photosynthesis by ammonia. Ammonia increased carbon traffic into organic acids and amino acids without affecting the total, ¹⁴C incorporation in the neutral fraction, although the relative distribution of ¹⁴C incorporation in the neutral fraction as a percentage of the total soluble ¹⁴C incorporation was decreased. The increased carbon flow into the amino acid fraction led to an increase of, ¹⁴C incorporation, principally into glutamine, glutamate, and aspartate. The role of ammonia in photosynthetic carbon metabolism is discussed.