H. Hartel et al., PHOTOSYNTHETIC LIGHT UTILIZATION AND XANTHOPHYLL CYCLE ACTIVITY IN THE GALACTOLIPID DEFICIENT DGD1 MUTANT OF ARABIDOPSIS-THALIANA, Plant physiology and biochemistry, 36(6), 1998, pp. 407-417
Photochemical and nonphotochemical light utilization was studied in th
e digalactosyl diacylglycerol-deficient dgd1 mutant of Arcrbidopsis th
aliana. While the contents of the photosynthetic metabolites and carbo
hydrates analyzed were found to be unchanged, chlorophyll fluorescence
quenching and xanthophyll-cycle activity were distinctly different in
the mutant. A decrease in the quantum yield of photosystem II electro
n transport under non-saturating photon flux densities in the dgd1 mut
ant was fully accounted for by an increase in nonradiative energy diss
ipation, measured as nonphotochemical fluorescence quenching (qN). Fur
thermore, the mutant showed a decreased amplitude of the fast relaxing
component of qN considered to reflect high-energy state quenching, bu
t displayed an increased slowly relaxing component of qN ascribed to p
hotoinhibition. The slowly relaxing qN component was correlated to per
sisting amounts of antheraxanthin and zeaxanthin, still present even a
fter prolonged dark exposure of previously illuminated leaves. Violaxa
nthin deepoxidation was found to be accelerated in the dgd1 mutant, bu
t the proportion of violaxanthin that becomes deepoxidized was similar
to that of the wild type. Our data suggest that xanthophyll-cycle ope
ration is involved in the reduction of the photosystem II quantum yiel
d in the dgd1 mutant. The results are discussed in terms of the altere
d thylakoid membrane organization of the dgd1 mutant. (C) Elsevier, Pa
ris.