Plant cell cultures are typically grown in media supplemented with 3% (w/v) sucrose and exhibit a non-green phenotype. I show that Arabidopsis thaliana cell cultures remain green even at 15% (w/v) sucrose when grown in the light and exhibit the major constituents of a normal photosynthetic apparatus. However, growth in the light was inhibited when no exogenous carbon source was provided. Gas exchange measurements indicated that rates of photosynthesis never exceeded rates of respiration. Thus, these green cells grow below their light compensation points. However, increasing sucrose concentration from 3% to 15% (w/v) decreased both photosynthetic efficiency and capacity. Furthermore, the green cells exhibit reversible photoacclimation. Energy partitioning measured by chlorophyll a fluorescence indicates that a large portion of the light energy absorbed is dissipated by both antennae and constitutive quenching mechanisms. The results are discussed in terms of sucrose sensing and its role in remodeling of the photosynthetic apparatus
