Hordeum; non-photochemical quenching; non-radiative dissipation; PAM fluorometer; photosystems 1 and 2

The effects of different spectral region of excitation and detection of chlorophyll (Chl) a fluorescence at room temperature on the estimation of excitation energy utilization within PS 2 were studied in wild-type barley and its mutant chlorina f2 grown under low and high irradiances. Three measuring regimes were applied using PAM 101 fluorometer: (1) excitation at 649 nm and detection in the far-red region beyond 710 nm, (2) excitation at 461 nm and detection beyond 710 nm, and (3) excitation in the blue region and detection in the red region (660?710 nm). Non-photochemical quenching of maximal (NPQ) and minimal fluorescence (SV0) were significantly higher for blue excitation as compared to red excitation. We suggest that this results from higher non-radiative dissipation of absorbed excitation energy within LHC2 due to its preferential excitation by blue radiation and from the lower contribution of PS1 emission to the detected fluorescence in the case of blue excitation.

The effects of different spectral region of excitation and detection of chlorophyll (Chl) a fluorescence at room temperature on the estimation of excitation energy utilization within PS 2 were studied in wild-type barley and its mutant chlorina f2 grown under low and high irradiances. Three measuring regimes were applied using PAM 101 fluorometer: (1) excitation at 649 nm and detection in the far-red region beyond 710 nm, (2) excitation at 461 nm and detection beyond 710 nm, and (3) excitation in the blue region and detection in the red region (660?710 nm). Non-photochemical quenching of maximal (NPQ) and minimal fluorescence (SV0) were significantly higher for blue excitation as compared to red excitation. We suggest that this results from higher non-radiative dissipation of absorbed excitation energy within LHC2 due to its preferential excitation by blue radiation and from the lower contribution of PS1 emission to the detected fluorescence in the case of blue excitation.