Are plants prone to curling up for a snooze, scientists wonder

PLANTS may need sleep at night as well as humans and animals, a new study has found.

Researchers have discovered the first evidence of sleep in a species without a brain, leading scientists to suspect the habit is fundamental to life itself, not just animals. The investigation focused on a primitive, spineless jellyfish that spends its entire life sitting upside down on the ocean floor, doing nothing more than occasionally pulsing.

A team from the California Institute of Technology closely monitored the Cassiopea species, finding it went through periods of relative inactivity during the night, pulsing only about 39 times a minute compared with 58 times during the day. The finding that this ancient organism sleeps implies that sleep began much earlier on the evolutionary timeline than previously thought, they said, meaning it could be shared across kingdoms.

“It may not seem surprising that jellyfish sleep – after all, mammals sleep, and other invertebrates such as worms and fruit flies sleep,” said Ravi Nath, who co-led the research. “But jellyfish are the most evolutionarily ancient animals known to sleep.

“This finding opens up many more questions: is sleep the property of neurons? And perhaps a more far-fetched question: do plants sleep?”

To be considered sleeping, an organism must show a period of reduced activity, and a decreased response to stimuli while in this state. Finally, it must demonstrate an increased need for sleep when deprived of it.

“We might seem extremely different from jellyfish, but we both exhibit a similar sleep state,” said Claire Bedbrook, who also worked on the study.

Earlier this year, Peter Wohlleben, an arboriculturist, claimed trees in Britain’s cities were dying early because the glare of street lights was interfering with their circadian rhythms and depriving them of “sleep”.