Abstract
Tobacco plants were subjected to long-term CO2 deficit. The stress caused photoinhibition of Photosystem (PS) II photochemistry and the aggregation of the light-harvesting complex of PS II (LHC II). The aggregation was shown by the appearance of the characteristic band at 698–700 nm (F699) in 77 K fluorescence emission spectra. LHC II aggregates are considered to quench fluorescence and, therefore, the fluorescence yield was determined to verify their quenching capability. PS II photochemistry, measured as FV/FM, was largely depressed during first 4 days of the stress. Unexpectedly, the total fluorescence yield increased in this period. Fitting of emission spectra by Gaussian components approximating emission bands of LHC II, PS II core, PS I and F699 revealed that mainly the bands at 680 and 699 nm, representing emission of LHC II aggregates, were responsible for the increase of the fluorescence yield. This shows an interruption of the excitation energy transfer between LHC II and both photosystems and, thus, a physical disconnection of LHC II from photosystems. PS II and PS I emissions were not quenched in this period. Therefore, it was concluded that these LHC II aggregates were accumulated out of PS II antenna, and, thus they cannot be involved in dumping of excess excitation. The total fluorescence yield turned to decrease only after the large depression of PS II photochemistry, when LHC II aggregation was considerably speeded up and the fluorescence yields of PS I and II turned to decline.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.