Stability of Arabidopsis P5CR . P5CR was partially purified by anion-exchange chromatography from crude extracts of an Arabidopsis cell suspension culture or E. coli strain BL21(DE3) (lon-, ompT-) and sterilised by filtration (0.22 μm pore size). The activity was assayed at increasing time during the subsequent storage at 25 ± 1°C under dim light. Results, expressed as percentage of activity at time 0, are mean ± SD over three independent replicates. The lines represent the exponential function that was generated by least square fitting and was used for calculation of the half-life time of the enzymes.