On the Reversal of the Inhibition of Photosynthesis Induced by Sodium Dimethyldithiocarbamate and Tetramethylthiuram disulphide

Abstract

AbstractThe reversal of 80–100 per cent inhibition of photosynthesis in the green alga Enteromorpha linza (L.) J. Ag., obtained with tetramethylthiuram disulphide (TMTD) and the corresponding sodium dithiocarhamate (Na‐DMDT), was investigated. The inhibition obtained by the two compounds proves to be almost completely reversible by simply washing away the inhibitors. Copper(II) sulphate partially reversed the inhibition obtained with Na‐DMDT while reduced glutathione (GSH) partially reversed inhibition obtained with both Na‐DMDT and TMTD. The time to complete the reversal varied between 12 and 33 min. Almost no reversal of the TMTD induced inhibition was achieved with CuSO4.Na‐DMDT and CuSO4 reacted instantaneously with each other. GSH most probably reduced TMTD stoichiometrically to DMDT. This reaction was complete‐ within 6 seconds. No reaction took place between GSH and Na‐DMDT.The interpretation of The results eliminates the most conventional explanation of the mechanism of the inhibition of photosynthesis in E. linza with Na‐DMDT, viz. complex formation with functional metals. The reaction between TMTD and functional thiol groups in the alga is the most plausible inhibition mechanism. It is inferred from the results that Na‐DMDT is most probably oxidized by E. linza to TMTD and effects inhibition in this form. (PDF DAMAGE)