Induction of chlorophyll fluorescence in Tradescantia leaves acclimated to growth light of different intensities

Fluorescence induction curves of Tradescantia fluminensis L. leaves acclimated to growth light of different intensities have been studied. Plants grown at low light (LL, 50–125 μmol photons m-2 s-1) and high light (875–1000 μmol photons m-2 s-1, HL) revealed different patterns of chlorophyll (Chl) a fluorescence. Chl fluorescence was measured by the PAMfluorometry method, using blue actinic light (455 nm, BAL) or red actinic light (630 nm, RAL). In the case of HL samples, non-photochemical quenching (NPQ) of Chl a fluorescence depended on actinic light intensity, but for all that we did not observe any difference between the samples illuminated by BAL or RAL. Otherwise, for leaves grown at LL conditions, we observed that BAL induced markedly higher NPQ than RAL. For both types of samples, photochemical quenching of fluorescence decreased with an increase in the intensity of actinic light, but in most cases was different upon the action of BAL and RAL. After switching the actinic light off, the NPQ level gradually decreased. The residual value of NPQ (qI), registered in the dark 30 min after ceasing AL, was dependent on the illumination pre-history. Maximal level of qI was observed in LL plants illuminated by BAL. The data obtained are discussed in the context of the problem of the protection of plant photosynthetic apparatus against solar stress.

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