Set an Alarm Clock for Bedtime? Plants Do, Chemically

New research suggests that plants come equipped with an inner circadian alarm clock that helps them survive the nights by regulating their energy consumption and metabolism in the evening.

Watching the Arabidopsis clock: Seedlings expressing a light emitting firefly gene controlled by the plant’s circadian rhythm. (Credit: Mike Haydon)

(CN) — Plants can rely on an internal circadian clock that helps them set “bedtimes” each evening when the supply of sunlight disappears, according to research released Monday.

Despite their small stature, plants are armed with an incredibly complex metabolic system that allows them to harvest, store and spend hard-earned energy for their survival. Perhaps the most well known cog in this plant metabolic network is their ability to convert light into sugars and other forms of energy through photosynthesis, a unique ability that allows plants to thrive in numerous environments.

But a plant’s reliance on sunlight has always presented one crucial question: what happens to a plant’s energy supply when night falls and sunlight becomes no longer available?

New insight into plant life reveals experts may have answered that very question.

In a study published Monday in the journal Proceedings of the National Academy of Sciences, researchers report that a key component to a plant’s ability to conserve energy and survive the darkness of each nightfall rests in what experts call the circadian clock. 

Circadian clocks are essentially chemical timekeepers each plant possesses that allows them to gauge the passage of time and the duration of their chemical reactions, a clock that gives them a rough idea of their daily routine every 24 hours.

Experts say like most clocks, these internal timepieces for plants also come with an alarm of sorts. Through an interconnected network of genes and other cells, researchers say that plants have an innate ability to adjust their clocks each night for the benefit of their own survival. 

Through this network they can predict the rising and falling of the sun, how long each night will last and estimate how much energy they need to conserve to make it to each morning.

This alarm, according to researchers, can single handedly tell plant life how to adjust their nightly metabolic schedule — and allocate their energy supply accordingly — every night with shocking precision.

“We think this metabolic signal is acting rather like setting an alarm clock before bedtime to ensure the plant’s survival,“ Mike Haydon, researcher at the University of Melbourne in Australia and one of the authors of the study, said in a statement. “Plants must coordinate photosynthetic metabolism with the daily environment and adapt rhythmic physiology and development to match carbon availability.”

The study reveals that experts came to this conclusion after experimenting with genes inside Arabidopsis, a small flowing plant related to cabbage and mustard plants.

In these plants, researchers discovered a collection of genes largely controlled by a special compound known as superoxide, a molecule often linked to a plant’s metabolism. 

Researchers found that when they restricted the creation of superoxide, they also restricted the influence sugar has on a plant’s clock and alarm system in the evening, establishing how a plant’s metabolic system is driven by its own inner timekeeper.

“Distinguishing the effects of light and sugars in photosynthetic cells is challenging,” Ian Graham from the Department of Biology’s Centre for Novel Agricultural Products said. “Our data suggest a new role for superoxide as a rhythmic sugar-related signal which acts in the evening and affects circadian gene expression and growth.”

Experts say this information helps to further flesh out our understanding of the complex processes that allow plants to grow and mature throughout Earth’s many ecosystems and helps to establish just how finely-tuned these natural mechanisms have evolved over time.

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