Excess copper predisposes photosystem II to photoinhibition in vivo by outcompeting iron and causing decrease in leaf chlorophyll.

Photoinhibition of photosystem II was studied in vivo with bean (Phaseolus vulgaris) plants grown in the presence of 0.3 (control), 4, or 15 microM Cu(2+). Although photoinhibition, measured in the presence of lincomycin to block concurrent recovery, is faster in leaves of Cu(2+)-treated plants than in control leaves, thylakoids isolated from Cu-treated plants did not show high sensitivity to photoinhibition.

Photoinhibition and loss of photosystem II reaction centre proteins during senescence of soybean leaves. Enhancement of photoinhibition by the 'stay-green' mutation cytG.

The 'stay-green' mutation cytG in soybean (Glycine max) partially inhibits the degradation of the light-harvesting complex II (LHCII) and the associated chlorophyll during monocarpic senescence. cytG did not alter the breakdown of the cytochrome b6/f complex, thylakoid ATP synthase or components of Photosystem I. In contrast, cytG accelerated the loss of oxygen evolution activity and PSII reaction-centre proteins.