DECREASE OF ENERGY-DEPENDENT QUENCHING, BUT NO MAJOR CHANGES OF PHOTOSYNTHESIS PARAMETERS IN ARABIDOPSIS-THALIANA WITH GENETICALLY-ENGINEERED PHOSPHATIDYLGLYCEROL COMPOSITION

Arabidopsis thaliana plants with genetically engineered strongly increased levels of 16:0/16:0 phosphatidylglycerol (PG) were analysed for the temperature dependence of photosynthesis. Despite a more than doubling of 16:0 fatty acid in the Cl position of PG, photosynthesis rates were practically identical in wild type (WT) and a transformant (T4) over the temperature range 5-35 degrees C. The same picture emerged for the temperature dependences of photochemical (q(P)) and different components of non-photochemical chlorophyll fluorescence quenching, near or at light saturation of photosynthesis, Under some conditions, i.e, at low temperatures and at low light intensities, the transformant revealed 0.1-0.2 U lower values of energy-dependent quenching (q(E)) than the WT. Under low photosynthetic light (40 mu E m(-2)s(-1)), maxima in the q(E) vs. T curves occurred at 8 degrees C, independent of PG composition. Chilling at 4 degrees C under periodical light for 7 days did not affect the photosynthetic activity of both WT and T4, while dark-chilled plants showed strong decreases of photosynthesis rates, q(P) and q(E). The PG composition only slightly affected the susceptibility of A. thaliana to photoinhibition at low temperature, and recovery from photoinhibition was unhampered by the altered lipid composition.