Xanthophyll-cycle dependence of the energy transfer between carotenoid dark states and chlorophylls in NPQ mutants of living plants and in LHC II

The Car S1 → Chl energy transfer efficiency, ΦTransfer, in xanthophyll-cycle mutants of living plants and LHC II was investigated by selective Car S1 two-photon excitation. Before high-light illumination ΦTransfer, of the violaxanthin deficient mutant npq2 is ∼30% smaller than the corresponding value for wild type plants. For the zeaxanthin deficient mutant, npq1, ΦTransfer is ∼30% larger. Wild type Arabidopsis thaliana is the only variant which is capable of a light-dependent decrease of up to 40% and complete recovery to the original ΦTransfer values. In contrast, ΦTransfer remains constant during dark adaptation in both mutants. Surprisingly, changes in ΦTransfer of LHC II preparations were less than 5% only, when substituting violaxanthin by zeaxanthin.