Photosynthesis in the biomass model species Lemna minor displays plant-conserved and species-specific features

Lemnaceae are aquatic freshwater plants with extraordinary high growth rates. We have studied selected physiological and molecular photosynthesis properties of the duckweed Lemna minor and compared these to the terrestrial model species Arabidopsis thaliana. Lemna and Arabidopsis plants grown under identical light intensities displayed similar photosynthesis characteristics, however, Lemna exhibited slighty better quenching efficiencies pointing to improved light utilization in the duckweed. Western-immuno-blot analyses of representative photosynthesis proteins suggest various post-translational modifications in Lemna that might be associated to this. Phospho-threonine phosphorylation patterns of thylakoid membranes uncovered differences between the two species. Testing the photosystem II antenna association of Lemna minor in dark and light by 77K chlorophyll fluorescence emission experiments, however, revealed a typical association as reported in terrestrial plants. High light stress experiments causing photoinhibition and subsequent recovery from it were not substantially different in Lemna when compared to Arabidopsis. We hypothesize that the molecular differences in Lemna photosynthesis proteins are associated with evolutionary adaptations to the aquatic life style and ultimately with the high growth rates. We also developed a video imaging approach for Lemna multiplication at high magnification that will be useful to assess the impact of external factors on Lemna photosynthesis and growth.