Identification of photosynthetic mutants of Arabidopsis by automatic screening for altered effective quantum yield of photosystem 2

Quantification of chlorophyll (Chl) fluorescence is a versatile tool for analysing the photosynthetic performance of plants in a non-intrusive manner. A pulse-amplitude modulated fluorometer was combined with a CNC router for the automated measurement of the effective quantum yield of photosystem 2 (Phi (2)) Of Arabidopsis thaliana plants. About 90 000 individual plants representing 7 500 lines derived from En-transposon and T-DNA mutagenised Arabidopsis populations were screened for mutants with altered Phi (2) Forty-eight recessive Phi (2) mutations were identified of which most exhibit also altered pigmentation and increased photosensitivity. For three Phi (2) mutants the corresponding mutated genes were identified that code all for chloroplast-located proteins. Comparison of the Phi (2) mutant screen with other screening methods based on die measurement of Chi fluorescence shows that the Phi (2) mutants identified are different to mutants identified by high Chi fluorescence. Some Phi (2) mutants, on the contrary, are common to mutants identified by screens based on non-photochemical quenching.