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 an alysing 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 re presenting 7 500 lines derived from En-transposon and T-DNA mutagenised Ara bidopsis populations were screened for mutants with altered Phi (2) Forty-e ight recessive Phi (2) mutations were identified of which most exhibit also altered pigmentation and increased photosensitivity. For three Phi (2) mut ants the corresponding mutated genes were identified that code all for chlo roplast-located proteins. Comparison of the Phi (2) mutant screen with othe r 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 mut ants identified by screens based on non-photochemical quenching.