The <i>gun5</i> mutant shows an enhanced but reversible phenotype after long term exposure to low temperatures.

<p>(a) 5 week old plants grown in short day condition (9/15 h light/dark, 22°C/18°C, 150 μE, control conditions) were transferred to 4°C, short day condition (9/15 h light/dark, 4°C/4°C, 150 μE) for 28 days. Bar represents 1 cm. (b) Transmission electron microscopy images of plastids from corresponding plants above. Bar represents 1 μm. (c) 5 week old plants were grown in SD conditions (150 μE) and transferred to SD conditions, 4°C (9/15 h light/dark, 4°C/4°C, 25 μE). After 28 days of cold exposure, plants were transferred back to control conditions for an additional 14 days for recovery.