Spectroscopic response of carotenoids in chromoplasts in sunflower inflorescence

The vibrant yellow color of the common sunflower (Helianthus annuus L.) ray flower ligules comes from the presence of xanthophylls. The dyes contained by chromoplasts of globular shape were identified in LC-MS studies as lutein derivatives, with lutein-5,6-epoxide as the major component. Ultrafast UV-vis spectroscopy revealed photoresponse of the xanthophylls in chromoplasts: photogenerated short-lived singlet excited S2 state population decays to the S1 state, which, subsequently repopulates carotenoids in the S0 ground state over 100 ps time window. In addition, the formation of an intermediate, proposed to be an entangled triplet state 1(TT), was also observed and explained by a singlet fission process occurring in aggregated xanthophylls in the chromoplasts. Light triggers photocycles in chromoplasts, which, from the macroscopic point of view means that light is converted to heat in sunflower inflorescence.