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 incre ased levels of 16:0/16:0 phosphatidylglycerol (PG) were analysed for t he temperature dependence of photosynthesis. Despite a more than doubl ing of 16:0 fatty acid in the Cl position of PG, photosynthesis rates were practically identical in wild type (WT) and a transformant (T4) o ver the temperature range 5-35 degrees C. The same picture emerged for the temperature dependences of photochemical (q(P)) and different com ponents 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 rev ealed 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 i n the q(E) vs. T curves occurred at 8 degrees C, independent of PG com position. Chilling at 4 degrees C under periodical light for 7 days di d 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 fr om photoinhibition was unhampered by the altered lipid composition.