Diethyldithiocarbamate, a New Photosystem I Electron Donor of Mehler-Type Hill Reactions*

Brad L. Upham and Kriton K. Hatzios Departm ent of Plant Pathology, Physiology and W eed Science, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061, USA Z. Naturforsch. 41c, 861 — 866 (1986); received April 10/May 20, 1986 Diethyldithiocarbamate, Photoreductant, E lectron D onor, Ascorbate, Superoxide Dismutase Diethyldithiocarbamate (D ED TC ) does not accept electrons from the photosynthetic electron transport (PET) but can donate electrons to a photosystem I (PSI) M ehler reaction in the pres­ ence of the following PET inhibitors: DCM U. DBM IB, and bathophenanthroline. It cannot photoreduce PSI in the presence of cyanide, a PET inhibitor. These data indicate that the site of electron donation is after the plastoquinone pool. Ascorbate is not required for the ability of D ED TC to donate electrons to PSI. There is no photoreductant activity by DEDTC inferredoxin/ NADP Hill reactions. Superoxide dismutase inhibits DEDTC/DCM U or bathophenanthroline m ethylviologen/02 Mehler reaction. Catalase does not recover the consumed 0 2 from a DEDTC/ DCMU —> m ethylviologen/02 M ehler reaction, indicating 0 2~ has not been dismutating into H20 2. These results indicate that superoxide is required for D ED TC ability to donate electrons, therefore D ED TC is limited only to Mehler-type reactions.