How do plants rest photosynthetic activity at night?
Photosynthesis, the process by which plants generate food, is a powerful piece of molecular machinery that needs sunlight to run. The proteins involved in photosynthesis need to be 'on' when they have the sunlight they need to function, but in the dark, when photosynthesis is not possible, they need to idle, like the engine of a car at a traffic light. They do this by a process called 'redox regulation'—the activation and deactivation of proteins via changes in their redox (reduction/oxidation) states. It's well understood that under sunlight, the ferredoxin-thioredoxin reductase (FTR)/thioredoxin (Trx) pathway is responsible for the reduction process, which activates the photosynthetic pathway. However, scientists have long been in the dark about what happens when light is not available, and how plants reset photosynthetic proteins to be ready to function when light is resumed.