PSI photoinhibition and protection at low temperatures and in fluctuating light: An 30 ecophysiological vista

In cucumber leaves at chilling temperatures below 10 degrees C, moderate constant light induces PSI photoinhibition with little effect on PSII.

• Why it matters: PSI was long considered resistant, but evidence shows chilling and fluctuating or pulsed light can damage PSI, with unclear causes, ROS sites, and functional consequences.
• What they did: This review compares cucumber chilling-induced PSI photoinhibition with PSI photoinhibition from fluctuating light or repetitive saturating pulses, tracking chloroplast changes, ROS production, and PSI damage.
• The result: It links PSI photoinhibition outcomes to where ROS arise and which PSI components are damaged, and highlights cyclic electron flow via NDH and PGR5/PGRL1 pathways as key suppressors.

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