What Plants Do During Night and Day: How a Plant is Active in the Dark

Most people know that plants photosynthesize during the day in order to create food to function. But what happens to plants at night? Scientists have taken a closer look, and have found that plants activate different biochemical pathways at night.

In this latest study, the researchers examined the photosynthetic alga, called Chlamydomonas. This alga has a protein called ferredoxin-5, which is apparently critical for growth in dark and for proper membrane organization.

The alga actually has several ferrodoxins. Interestingly, though, a mutant version of the alga without ferrodoxin-5 was unable to grow in the dark, or perform normal metabolic functions. However, it had no trouble growing in the daytime.

The membranes are made up of lipids, which are fatty acids linked to a glycerol backbone. The ferrdoxin-5 mutant actually shows marked alterations in the bond structure of many of these fatty acids, which changes the degree of saturation in the fatty acids present in the membranes. This, in turn, impacts the lipid composition of the membranes and results in aberrant membrane structure that impairs metabolic processes, including photosynthesis, that occur on those membranes.

The findings suggest that one of the biochemical reactions that ferredoxin-5 drives through its electron-donating abilities is this alteration in the saturation state of fatty acids. This result indicates that when the alga is in the dark, ferredoxin-5 specifically donates electrons to enzymes that specialize in desaturating fatty acids. It may also donate electrons to other processes in the dark.

The findings reveal a bit more about the role of ferredoxin-5, and show what happens to photosynthesizing organisms when it turns from light to dark.

The findings are published in the journal Proceedings of the National Academy of Sciences.

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