V. Spunda et al., REGULATION OF PHOTOCHEMICAL EFFICIENCY OF PHOTOSYSTEM-2 IN NORWAY SPRUCE AT THE BEGINNING OF WINTER AND IN THE FOLLOWING SPRING, Photosynthetica, 33(1), 1997, pp. 91-102
Based on the analysis of fluorescence quenching, the nonphotochemical
dissipative processes were investigated in Norway spruce needles durin
g acclimation to winter and spring conditions. The maximum nonphotoche
mical fluorescence quenching (q(Nmax)) was reached at lower irradiance
s in winter (up to 310 mu mol m(-2) s(-1)) than in spring (about 1130
mu mol m(-2) s(-1)), but its values were nearly the same (q(Nmax) = 0.
91+/-0.01) during both winter and spring measurements. In early winter
the pronounced initial fluorescence quenching (q(0)) suggested that n
onradiative energy dissipation in the antennae complexes dominated. Si
gnificantly lower q(0) (by 40-60 % compared to winter needles) during
acclimation of needles to spring conditions supported a significant co
ntribution of quenching in the reaction centres, These findings suppor
t the hypothesis that the antennae systems and reaction centres cooper
ate in the protective dissipation of excess excitation energy.