False color images of chlorophyll fluorescence yield (FV/FM) of Arabidopsis leaves (accession C24 after cold acclimation) after freezing to different temperatures. For the color scale, see Fig. 1. At each temperature, images from three replicate leaves are shown. Leaves were either imaged directly after thawing (no incubation), or after 24 h of incubation in distilled water at 4°C (24 h incubation), corresponding to the treatment of leaves prior to electrolyte leakage measurement.