Comparative Study of the Inhibition of Photosynthesis Caused by Aminooxyacetic Acid and Phosphinothricin in Zea mays

Summary Maize plants fed with PPT (a glutamine synthetase inhibitor) accumulate ammonia. Approximately 50 % of the ammonia accumulated seems to come from the photorespiratory pathway, while the nonphotorespiratory ammonia is derived from nitrate reductase activity. The ammonia accumulated, however, is not sufficient to increase GDH activity. We also carried out a comparative study of the effect of PPT and AOA on photosynthesis. Both compounds inhibit the photorespiratory pathway, causing glycolate accumulation and diminishing photosynthesis.