Seasonal changes of excitation energy transfer and thylakoid stacking in the evergreen tree Taxus cuspidata: How does it divert excess energy from photosynthetic reaction center?

Abstract

Photosystems must efficiently dissipate absorbed light energy under freezing conditions. To clarify the energy dissipation mechanisms, we examined energy transfer and dissipation dynamics in needles of the evergreen plant Taxus cuspidata by time-resolved fluorescence spectroscopy. In summer and autumn, the energy transfer processes were similar to those reported in other higher plants. However, in winter needles, fluorescence lifetimes became shorter not only in PSII but also in PSI, indicating energy dissipation in winter needles. In addition, almost the same fluorescence spectra were obtained with different excitation wavelengths. In contrast, the fluorescence spectrum showed a large difference due to excitation wavelength in spring needles. The fluorescence spectrum of spring needles in 550-nm excitation showed similar spectra to that of winter needles, however, red-chlorophyll fluorescence was not observed in chlorophyll excitation. These observations suggest that some complexes with some kind of red-shifted carotenoid and red-chlorophyll unlink from the core complex in spring. Seasonal changes of excitation energy dynamics are also discussed in relation to changes in thylakoid stacking.

pH-Sensing Machinery of Excitation Energy Transfer in Diatom PSI–FCPI Complexes

“…A pair of positive and negative amplitudes reflects energy transfer from a pigment with positive amplitudes to one with negative amplitudes. 27,28 It should be noted that when negative or positive peaks are superimposed by higher magnitudes of positive or negative peaks, respectively, a FDA spectrum does not necessarily exhibit a set of positive and negative peaks. 29 The pH 6.5 FDA spectra of the PSI−FCPI and PSI are virtually identical to those reported recently.…”

Acidic pH-Induced Modification of Energy Transfer in Diatom Fucoxanthin Chlorophyll a/c-Binding Proteins

“…Under the pH-6.5 condition, the 50 ps FDA spectrum exhibits a set of a positive peak at 671 nm and a negative peak at 681 nm. Because a pair of positive and negative peaks reflects energy transfer from a pigment with positive amplitudes to one with negative amplitudes, , the peak set in the 50 ps FDA spectrum suggests energy transfer from the Chl fluorescing at 671 nm to that at 681 nm. The 2.6 ns FDA spectrum showed a positive peak at 675 nm.…”

Structural basis for different types of hetero-tetrameric light-harvesting complexes in a diatom PSII-FCPII supercomplex

“…Fluorescence rise and decay components are depicted in positive and negative peaks, respectively. A pair of positive and negative amplitudes reflect excitation-energy transfer from a pigment with a positive amplitude to one with a negative magnitude 33 , 34 . In the case of a sequential energy transfer of A→B→C (e.g., A, B, and C represent pigments), clear positive and negative bands appear only for A and C, respectively, whereas the negative amplitude of B (A→B transfer) is canceled by the positive one of B (B→C transfer) in the same FDA spectrum.…”