We have investigated the function of the chlorophyll a/b binding proteins CP26 and CP24 in light harvesting and energy dissipation. Analysis of chlorophyll fluorescence showed that removal of these photosystem II antenna proteins affected the photosynthetic function yielding decreased electron transport rates, reduced qE and limited growth in kolhcb6 plants but not in kolhcb5 plants. Surprisingly, the double mutant kolhcb6x kolhcb5 showed overall electron transport, and amplitude of qE similar to wild type. We conclude that CP24 protein is not directly involved in the NPQ process. The decrease of NPQ and the limited growth rate in koLhcb6 appear to be caused by a limitation in plastoquinone diffusion within grana stacks which causes decreased proton pumping into the lumen.
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