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Dithiothreitol, an inhibitor of violaxanthin de-epoxidation, increases the susceptibility of leaves ofNerium oleander L. to photoinhibition of photosynthesis.

Abstract：

:Leaves ofNerium oleander L. plants, which had been previously kept in a shaded glasshouse for at least two months, were fed 1 mM dithiothreitol (DTT) through their petioles, either for 12h in darkness (overnight) or for 2h in low light (28 μmol photons·m(-2)·s(-1)), in each case followed by a 3-h exposure to high light (1260 μmol photons·m(-2)·s(-1)). During exposure to high light, violaxanthin became converted to zeaxanthin in control leaves, to which water had been fed, whereas zeaxanthin did not accumulate in leaves treated with DTT. Total carbon gain was not reduced by DTT during the photoinhibitory treatment. Exposure to high light led to a decrease in the photochemical efficiency of photosystem II, measured as the ratio of variable over maximum fluorescence emission,F v/F M, at both 298 K and 77K. The decrease was much more pronounced in the presence of DTT, mainly owing to a sustained increase in the instantaneous fluorescence,F o. By contrast, in the control leaves,F o determined immediately after the high-light treatment showed a transient decrease below theF o value obtained before the onset of the photoinhibitory treatment (i.e. after 12 h dark adaptation), followed by a rapid return (within seconds) to this original level ofF o during the following recovery period in darkness. Incubation of leaves with DTT led to large, sustained decreases in the photon-use efficiency of photosynthetic O2 evolution by bright light, whilst the capacity of photosynthetic O2 evolution at light and CO2 saturation was less affected. In the control leaves, only small reductions in the photon yield and in the photosynthetic capacity were observed. These findings are consistent with previous suggestions that zeaxanthin, formed in the xanthophyll cycle by de-epoxidation of violaxanthin, is involved in protecting the photosynthetic apparatus against the adverse effects of excessive light.

journal_name

Planta

journal_title

Planta

authors

Winter K,Königer M

doi

10.1007/BF02411406

subject

Has Abstract

pub_date

1989-12-01 00:00:00

pages

24-31

issue

eissn

0032-0935

issn

1432-2048

journal_volume

180

pub_type

杂志文章

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Dithiothreitol, an inhibitor of violaxanthin de-epoxidation, increases the susceptibility of leaves ofNerium oleander L. to photoinhibition of photosynthesis.