Fig. 4. los2 plants are defective in membrane integrity under light and cold treatment. (A) Ion leakage assay. Wild-type and los2 mutant leaves from 3-week-old plants grown in soil were used for the assay. For cold acclimation (CA), plants were incubated at 4°C for 2 days under light (20 µmol/m2/s) before the ion leakage assay. Shown are the mean values and standard errors from three replicates. (B) Protoplast shrinkage and plasma membrane damage revealed by transmission electron microscopy. Leaves from wild-type and los2 plants incubated at 4°C for 2 days under light (20 µmol/m2/s) are shown. Bar = 1 µm. CW, cell wall; PM, plasma membrane; N, nucleus; CH, chloroplast. The gray arrow indicates broken plasma membrane in los2 leaf cells. The white arrow indicates membrane blebbing in los2 leaf cells.