title: Time-resolved spectroscopic fluorescence imaging, transient absorption and vibrational spectroscopy of intact and photo-inhibited photosynthetic tissue.
abstract: Fluorescence, absorption and vibrational spectroscopic techniques were used to study spinach at the photosystem II (PS II), chloroplast and cellular levels and to determine the effects and mechanisms of ultraviolet-B (UV-B) photoinhibition of these structures. Two-photon fluorescence spectroscopic imaging of intact chloroplasts shows significant spatial variations in the component fluorescence spectra in the range 640-740 nm, indicating that the type and distribution of chlorophylls vary markedly with position in the chloroplast. The chlorophyll distributions and excitonic behaviour in chloroplasts and whole plant tissue were studied using picosecond time-gated fluorescence imaging, which also showed UV-induced kinetic changes that clearly indicate that UV-B induces both structural and excitonic uncoupling of chlorophylls within the light-harvesting complexes. Transient absorption measurements and low-frequency infrared and Raman spectroscopy show that the predominant sites of UV-B damage in PS II are at the oxygen-evolving centre (OEC) itself, as well as at specific locations near the OEC-binding sites.
authors.affiliation: School of Physics, University of Sydney, NSW 2006, Australia. Philip.Lukins@measurement.gov.au
authors.forename: Philip B
authors.initials: PB
authors.lastname: Lukins
authors.forename: Shakil
authors.initials: S
authors.lastname: Rehman
authors.forename: Gregory B
authors.initials: GB
authors.lastname: Stevens
authors.forename: Doaa
authors.initials: D
authors.lastname: George
mesh_terms: D002734:Chlorophyll / Q000032:analysis; D002736:Chloroplasts / Q000737:chemistry / Q000528:radiation effects*; D045332:Photosystem II Protein Complex / Q000737:chemistry / Q000528:radiation effects*; D013050:Spectrometry, Fluorescence; D017550:Spectroscopy, Fourier Transform Infrared; D013057:Spectrum Analysis; D013059:Spectrum Analysis, Raman; D018724:Spinacia oleracea; D013995:Time; D014466:Ultraviolet Rays
chemical_list: D045332:Photosystem II Protein Complex; D002734:Chlorophyll