Action of mercury on the photosynthetic apparatus of spinach chloroplasts

In chloroplasts of Spinacea oleracea L., Hg2+ ions interact with some sites in the photosynthetic electron transport chain: (I) with the intermediates Z(+)/D+ situated in the D1 and D2 proteins and with the manganese cluster in the oxygen evolving complex which are located on the donor side of photo system (PS) 2, (2) with the chlorophyll a dimer in the core of PSI (P700). P700 is oxidized in the dark by HgCL2. The Hg2+ ions form organometallic co mplexes with amino acids contained in chloroplast proteins.