Effect of EMD‐IT‐5914 on Chlorophyll Synthesis in Leaves of Pennisetum typhoides Seedlings

EMD‐IT‐5914 (5‐dimethylamino‐methylene‐2‐oxo‐4‐phenyl‐2,5‐dihydrofurane‐carbonitril‐(3)) inhibited chlorophyll a formation almost completely and chlorophyll b and total carotenoids up to 80% of the control, but did not appreciably affect the activity of the enzyme system succinyl‐CoA synthetase/δ‐aminolevulinic acid synthetase. The activity of δ‐aminolevulinic acid dehydratase was not found limiting. In contrast, the herbicide strongly inhibited the activity of porphobilinogenase, and the reaction kinetics pointed towards a non‐competitive type of inhibition. The results are discussed in relation to the possible role of EMD‐IT‐5914 in chlorophyll biosynthesis.