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An examination of factors contributing to non-photochemical quenching of chlorophyll fluorescence in barley leaves

1989; Elsevier BV; Volume: 977; Issue: 3 Linguagem: Inglês

10.1016/s0005-2728(89)80082-9

1879-2650

W. Paul Quick, Mark Stitt,

Plant responses to elevated CO2

The 'dark' relaxation of the non-photochemical quench in leaves has been monitored by applying short saturating pulses of light, and measuring the yield of chlorophyll fluorescence. The non-photochemical, quench relaxes with complex kinetics, revealing at least three components with half-times of about 1 min ('fast'), 5 min ('middle') and hours ('slow'). The 'fast' component only appears after illumination with high actinic light. This component also relaxes after switching to low actinic light, or if light pulses are applied in the 'dark'. It is selectively increased with tentoxin and decreased by nigericin, and is identified as high-energy state quenching (qE). Very high light intensities are needed to saturate the fluorescence yield during light, pulses when this component is present. The 'middle' component is saturated by relatively low actinic light intensities. The 'middle' component is affected by changing the light quality, when it correlates with a readjustment of QA oxidation, and it can be abolished by fluoride. It is associated with the redistribution of excitation energy (state transitions, qT). The remaining 'slow' phase has a residual component at low light and increases markedly after illumination with very high light intensities. This component is attributed to photoinhibitory processes (q1). It is discussed how qE makes a very variable, and often small, contribution to non-photochemical quenching in leaves.