Plants’ internal clocks keep them alive at night and ‘could be key to growing more food for the world’

The finding sheds new light on how life on our planet is in tune with the movements of the solar system, writes Harry Cockburn

‘Plants can’t stumble to the fridge in the middle of the night’ (Getty Images/500px Plus)

Just like animals, plants’ lives are dictated by the rising and setting of the sun.

The circadian rhythm is a vital part of plants’ ability to time key processes allowing them to adjust their biology – from producing oxygen and absorbing carbon, to flowering, leaf movement and even producing fragrances.

But plants’ ability to recognise and adjust to changing times of day and night and the seasons is more than a handy adaptation. It can be a matter of life and death, and could even lead to greater levels of food production, new research suggests.

Scientists at the University of York and the University of Melbourne studied the arabidopsis flower – a member of the mustard family – and discovered it uses what they described as “a biological time-keeper” to survive the night.

During the day, plants use the available sunlight to make their own sugars through photosynthesis, and store them to maintain an energy supply during the night.

They found the plants produce a metabolic signal at exactly the right moment which adjusts their circadian clock in the evening, ensuring enough energy is conserved to survive the dark hours when the plant cannot photosynthesise.

This process involves a set of genes known to be regulated by the chemical compound superoxide, a molecule associated with metabolic activity, the scientists said.

The finding reveals for the first time how plants’ metabolic processes stay in tune with the passage of time, helping them “know when to grow”.

The scientists said this understanding could help humans grow crops in different environments, seasons, latitudes or even in artificial environments and vertical gardens.

Lead researcher Dr Mike Haydon, of the University of Melbourne’s School of BioSciences, said: “Getting the timing of this daily cycle of metabolism right is really important because getting it wrong is detrimental to growth and survival.

“Plants can’t stumble to the fridge in the middle of the night if they get hungry so they have to predict the length of the night so there’s enough energy to last until sunrise - a bit like setting an alarm clock.”

The researchers had earlier shown that the accumulation of sugars produced from photosynthesis help give plants important information about the amount of sugar generated in the morning and allows them to adjust their pace.

“We have now found that a different metabolic signal, called superoxide, acts at dusk and changes the activity of circadian clock genes in the evening,” said Dr Haydon.

“We also found that this signal affects plant growth. We think this signal could be providing information to the plant about metabolic activity as the sun sets.”

The researchers said they hope the study will become invaluable in efforts to produce more food, more reliably.

Professor Ian Graham, from the University of York, added: “Distinguishing the effects of light and sugars in photosynthetic cells is challenging.

“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.”

Despite being considered a weed, the arabidopsis flower was the first in the world to have its genome sequenced, and it remains a popular species for understanding the molecular biology of many plant traits, including flower development and light sensing.

The research is published in the PNAS journal.