Hierarchy amongst photosynthetic acclimation responses for plant fitness

We have compared the seed production of Arabidopsis wild‐type and mutant plants impaired in the regulation of the photosynthetic light reactions grown under natural conditions in the field. Mutant plants ( npq4 ) lacking feedback de‐excitation were, as previously demonstrated, severely affected in seed production. Seed sets of plants deficient in state transitions ( stn7 ) were 19% smaller than those of wild‐type plants, whereas plants missing the STN8 kinase required for the phosphorylation of the core photosystem II reaction centre polypeptides ( stn8 ) had a normal seed production. Plants lacking both STN7 and STN8 kinases were strongly affected, indicating that these mutations act synergistically. In contrast, npq4 × stn7 double mutants had the same seed set as npq4 mutants.