How to translate text using browser tools
1 October 2000 Inhibition of Photosynthetic Electron Transport by UV-A Radiation Targets the Photosystem II Complex
Enikö Turcsányi, Imre Vass
Author Affiliations +

We have studied the inhibition of photosynthetic electron transport by UV-A (320–400 nm) radiation in isolated spinach thylakoids. Measurements of Photosystem II (PSII) and Photosystem I activity by Clark-type oxygen electrode demonstrated that electron flow is impaired primarily in PSII. The site and mechanism of UV-A induced damage within PSII was assessed by flash-induced oxygen and thermoluminescence (TL) measurements. The flash pattern of oxygen evolution showed an increased amount of the S0 state in the dark, which indicate a direct effect of UV-A in the water-oxidizing complex. TL measurements revealed the UV-A induced loss of PSII centers in which charge recombination between the S2 state of the water oxidizing complex and the semireduced QA and QB quinone electron acceptors occur. Flash-induced oscillation of the B TL band, originating from the S2QB recombination, showed a decreased amplitude after the second flash relative to that after the first one, which is consistent with a decrease in the amount of QB relative to QB in dark adapted samples. The efficiency of UV-A light in inhibiting PSII electron transport exceeds that of visible light 45-fold on the basis of equal energy and 60-fold on the basis of equal photon number, respectively. In conclusion, our data show that UV-A radiation is highly damaging for PSII, whose electron transport is affected both at the water oxidizing complex, and the binding site of the QB quinone electron acceptor in a similar way to that caused by UV-B radiation.

Enikö Turcsányi and Imre Vass "Inhibition of Photosynthetic Electron Transport by UV-A Radiation Targets the Photosystem II Complex," Photochemistry and Photobiology 72(4), 513-520, (1 October 2000).<0513:IOPETB>2.0.CO;2
Received: 14 June 2000; Accepted: 1 July 2000; Published: 1 October 2000

This article is only available to subscribers.
It is not available for individual sale.

Get copyright permission
Back to Top