Do Plants Sleep? (Understanding Sleep-Like Behavior in Plants)

As the sun goes down, the biological world undergoes some important changes. Nocturnal animals will wake up, while diurnal animals will go to sleep. It’s very easy to observe sleeping patterns in animals, but plants are extremely different organisms. So do plants sleep?

Plants don’t sleep but do show a certain behavior that resembles sleep in animals. Plants will stop photosynthesizing and most plants will close their stomata. However, plants still stay active during the night and some plants will even open their stomata at night.

Plants and animals are extremely different organisms with distinct physiological and biological processes. The sleeping behavior of animals even differs from animal to animal. Did you know that even in the animal kingdom there exist animals that sleep less than an hour a day?

Although plants don’t have a central nervous system and can’t sleep, they have a circadian rhythm. Plants will also show differences in daytime and nighttime activity. This accounts for sleep-like behavior.

In this article, you’ll learn what sleep is and what kind of sleeping behavior occurs in plants. You’ll learn why we can’t speak of sleep in a traditional definition in the plant kingdom.

What is Sleep?

According to Wikipedia sleep can be defined as “a naturally recurring state of mind and body, characterized by altered consciousness, relatively inhibited sensory activity, reduced muscle activity and inhibition of nearly all voluntary muscled during rapid eye movement sleep, and reduced interaction with surroundings.”

Sleeping requires an animal or organism to have a central nervous system. The biological process is regulated by a series of mechanisms and neurotransmitters in our brain. Common problems with sleeping can be attributed to problems in the central nervous system.

Scientists have also noted some characteristics that accompany sleep:

• typical (sleeping) posture
• relatively easy to reverse (contrary to hibernation and coma)
• period of reduced activity
• decreased response to external stimuli

Do Plants Sleep?

The definitions of sleep that are available only make it possible for humans and animals to experience “sleep”. Plants lack a central nervous system and aren’t capable of sleep.

Although plants don’t have a central nervous system and can’t sleep, they exhibit behavior that can be interpreted as sleep-like behavior. In particular, plants:

• show changes in activity during the night
• have a 24-hour biological clock (circadian rhythm)

Do plants sleep at night?

When we think of sleep, we think of nighttime. Of course, not all animals sleep during the night. There are diurnal, crepuscular, and nocturnal animals:

• diurnal animals: active during the day and sleep during the night;
• nocturnal animals: active during the night and sleep during the day;
• crepuscular animals: more active during twilight( dusk and dawn).

We know that plants photosynthesize during the day, so do they sleep or show reduced activity during the night? Plants indeed show reduced activity and a change in activity during the night. This could be interpreted as sleep-like behavior.

Sleep-like behavior during the night

As I already mentioned, plants don’t sleep in the same way as we or other animals do. But you can’t deny that there are changes in plant behavior that indicate a change in nighttime activity:

• photosynthesis will stop and chloroplasts will shrink in size
• most plants will close their stomata (used to absorb carbon dioxide)
• a lot of plants will move their leaves in a resting position
• daytime bloomers will close their flowers at night

Nighttime metabolic shifts

During the night, there are metabolic changes in the plant. Plants have photosynthesized during the day and will start consuming the energy that was stored during the day.

Plants have very sophisticated circadian rhythms that control the production and consumption of this nighttime feeding to adapt to seasonal changes in light. The controls make sure that a plant doesn’t over-prepare for short summer nights and don’t go hungry during long winter nights.

Like us, plants also undergo important healing processes at night involved in repairing cells and tissues damaged during the day from UV light, environmental pollutants, and harmful metabolic byproducts. Experiments conducted where plants were exposed to artificial nighttime lights showed that they were unable to recover from these damages caused by daytime stresses.

Plants are still active during the night

Although plants show sleep-like behavior during the night, they are still very active. The nighttime energy reserves are consumed by the plant to have the energy for the basic metabolic activity, but the plant will also use the energy to grow above and below ground

Some plants also open their stomata at night, contrary to the behavior of other plants. Plants in an environment that doesn’t have a lot of water will open their stomata at night to absorb carbon dioxide. During the day these plants keep their stomata closed to reduce water loss.

Other plants wait till the darkness of night to bloom, releasing fragrant aromas into the air to attract bats, sphinx moths, and other nocturnal pollinators. In some ways, the activity of plants is not always reduced in nighttime hours.

Do plants sleep in the winter?

Another behavior that can be interpreted as sleep is the state of dormancy of plants during the winter months in northern latitudes. Although dormancy may look like sleeping isn’t the same and should not be misinterpreted as such. So, plants don’t sleep in the winter but may enter a state of dormancy (stopped metabolic activity).

When plants go into a state of dormancy, the metabolic activity stops completely. Deciduous plants, plants that seasonally lose their leaves, will drop their leaves and won’t be able to photosynthesize without them. Evergreen species, like pines, also enter into dormancy.

Since the state of dormancy isn’t easily reversible and lasts for a longer period, it can’t be compared with sleep. It could be compared to hibernating animals although in a strict sense plants don’t “hibernate”.

Want to Learn More?

If you want to learn more interesting facts about plants, you should definitely read the following articles:

• Are plants producers?
• Can plants get cancer?

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