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Chlorophyll fluorescence and antioxidative capability in detached leaves of the wild type Arabidopsis thaliana L. ecotype Landsberg erecta ( Ler) and three mutants deficient in anthocyanins biosynthesis ( tt3, tt4, and tt3tt4) were investigated during treatment with temperatures ranging 25–45 °C. In comparison with the wild type, chlorophyll fluorescence parameters Fv/Fm, ΦPSII, electron transport rate (ETR), Fv/Fo and qP in three anthocyanin-deficient mutants showed a more rapidly decreasing rate when the temperature was over 35 °C. Non-photochemical quenching (NPQ) in these mutants was almost completely lost at 44 °C, whereas the content of heat stable protein dropped and the rate of the membrane leakage increased. Fo-temperature curves were obtained by monitoring Fo levels with gradually elevated temperatures from 22 °C to 72 °C at 0.5 °C/min. The inflexion temperatures of Fo were 45.8 °C in Ler, 45.1 °C in tt3, 44.1 °C in tt4 and 42.3 °C in tt3tt4, respectively. The temperatures of maximal Fo in three mutants were 1.9–3.8 °C lower than the wild type plants. Meanwhile, three mutants had lower activities of superoxide dismutase (SOD) and ascorbate peroxidase (APX) and an inferior scavenging capability to DPPH (1.1-diphenyl-2-picrylhy.drazyl) radical under heat stress, and in particular tt3tt4 had the lowest antioxidative potential. The results of the diaminobenzidine-H2O2 histochemical staining showed that H2O2 was accumulated in the leaf vein and mesophyll cells of mutants under treatment at 40 °C, and it was significantly presented in leaf cells of tt3tt4. The sensitivity of Arabidopsis anthocyanins-deficient mutants to high temperatures has revealed that anthocyanins in normal plants might provide protection from high temperature injury, by enhancing its antioxidative capability under high temperature stress. [ABSTRACT FROM AUTHOR]