Children ask a lot of questions in their quest to learn things about the world around them. While you may be able to answer questions about why cats purr or how birds fly, some questions like whether plants sleep can stump you.
Do plants sleep? It's a simple question, but the answer isn't quite as simple to answer. Many people may guess the answer is yes, but is it? Every living thing needs rest but do plants get tired and need to relax and take a nap too?
While many plants go dormant during the winter when it's cold outside, houseplants have protection from the cold, snow, and ice all year round. So, their growth may slow but not stop altogether. However, that doesn't answer the question about whether they sleep. Fortunately, the rest of the information that you'll read here can help you find out.
DO Plants require sleep?
Plants work tirelessly to create the food they need, which comes in the form of carbohydrates, sugars, and starches, during the photosynthesis process. Plants use over 90 percent of their energy on this chore alone. So, you would think they need to rest to regain the energy they use during this process.
However, unlike humans, plants don't have a central nervous system that helps them regulate sleep. They are tuned in to the same circadian rhythms that humans use. Also, when the sun goes down in the evening, some of their processes like photosynthesis shuts down because it requires sunlight to work.
A plant’s system uses cues to shut down some processes when the sun goes down and begin others. They have a hormone called auxin that is triggered by changes during the day when the sun goes down, and it gets dark. During this change in light, auxin controls the plant’s development and growth.
what is the circadian rhythm?
To answer, “Do plants sleep?” we first must understand the circadian rhythm. The circadian rhythm is a 24-hour cycle that occurs in the physiological processes of most living beings, including humans, plants, cyanobacteria, and fungi. While it is internal, sunlight and nighttime regulate a plant's circadian rhythm. In humans, when the sun goes down, and nighttime emerges, it activates melatonin, and we begin to get sleepy.
In plants, their daytime processes, like photosynthesis, shut down, and their systems prepare for energy consumption that causes them to grow. In some plants, the circadian clock they have adjusts their chemical processes to defend themselves from predators. For instance, some plants launch chemical attacks that can make their leaves or fruit repulsive to predatory insects.
Circadian clocks are most noticeable in outdoor plants because some flowers, like those of the sunflower, follow the sun by moving its head as the sun moves. Other flowers, like the morning glory, closes its petals when the sun goes down. In houseplants, the changes triggered by their circadian rhythms are not as noticeable, but a recent study found that they do occur.
Studying Plant Movement Using TLiDAR
Scientists in the Netherlands used a laser to measure the movement of plant leaves during the day and night to find out if their circadian clocks influence the plants' movement. TLiDAR is a remote detecting technique that gives accurate distance measurements using lasers, which also times the return energy. LiDAR stands for Light Dictation and Ranging.
The results of the study found that the leaves of plant one in the experiment, which was in natural light conditions, grew in volume in the daytime by over seven centimeters and the angle changed by almost 70 degrees. Most of the activity took place during the morning around seven in the morning to 12:30 in the afternoon.
The results of plant two, which was growing in the darkness, confirmed the activity of plant one. Most of its changes occurred in the morning, showing that it isn't the presence of light that triggers a plant's responses, but their internal circadian clocks that turn off processes and switches to growth mode.
Reaching for sunlight
These experiments show that when houseplants are growing in low-light conditions, they instinctively reach for sunlight, not because of its presence, but because their internal circadian clocks trigger them to do so.
To better the health of indoor plants, it is essential to expose them to as much light as possible without overheating or drying them out. The best way to do so may be to water them and then hang them outside on the porch or set them on the stoop early in the morning and bring them in by midday.
If you leave them out, try to find a spot where they can get some shade in the afternoon as their clocks begin the process of shutting down as evening approaches. Doing this can keep plants from getting too hot or drying out too much during the day. Then, when you get home, you can give them a bit more water if they need it.
The role of ethylene
Ethylene is a gas that plants produce to help ripen their fruit. If you have a ripening banana and an unripe avocado, you can see how ethylene works by putting the avocado next to the banana. The gas produced during the banana's ripening process will help the avocado ripen as well. This process is one way that plants communicate with each other.
The communication between plants can help ensure that all fruits on a tree or an orchard of trees, ripen at the same time. Collaboration experiments meant to explore the role of plant genes and proteins in regulating circadian clocks found that ethylene is the key to maintaining a plant’s circadian rhythm.
Multiple experiments were able to show that plants' circadian rhythms continue to work even after harvesting the fruit from the plants. So, even after cutting bananas from trees or picking tomatoes from vines, they still have living cells.
To keep the fruit at its best, scientists suggest allowing it to stay in a natural state because any stresses on plants release ethylene, which can age or continue to ripen them. These experiments also show that by manipulating ethylene production and disrupting plants circadian clocks, crops may produce higher food yields.
Night is as important as day
To indoor plants, what they do at night is just as important as what they do during the day. During the daylight hours, they use the sunlight they receive to create carbohydrates, their food source. At night is when they metabolize the food and use it as energy to grow.
Houseplants can experience disruptions in this process if grow lights are on because they can disrupt the plants’ circadian clocks by coming on at the wrong time or staying on too long. Not being able to "rest," which comes down to not being able to perform their nightly duties, can stunt the growth of plants.
Their root systems will not grow as big and robust as they should and the crops that the plants produce, such as seeds or pods, may fail to grow. Plants need a break from light, which can be difficult if they are in areas where the lights are on past nighttime hours, such as a living room or bedroom. Even the presence of television lights may disrupt their internal clocks.
If you have an area in which most of your plants grow, try not to enter it at night. However, if that isn’t possible due to their location, consider using green spectrum LED lighting in an indoor green environment. However, for houseplants in areas that get irregular lighting at night, the good news is that the circadian rhythms in plants can adjust to different light schedules.
Another experiment from Danish scientists revealed that plants were able to adjust from their regular day/night schedules to irregular lighting situations, specifically exposure to supplemental or low-light, exposure at night. The results of the expert showed that the plants’ leaves and stems grew faster under the supplemental light exposure than they did under normal lighting conditions.
So, the plants were able to adapt and grow healthy, which means your houseplants can as well. Don't purposely expose plants to light at night unless you're unable to control it. Light from a fish tank may need to be on or a nightlight in the hallway for a child.
By giving your plants a break from light, you will help them maintain their natural sequences of creating food during the day and metabolizing it at night. Maintaining their natural schedules can help produce healthy growth that will form beautiful foliage and blooms on your plants.
If your house or apartment tends to be dark due to the lack of windows, try to set the plants outside during the morning hours to get them the exposure to sunlight that they need. A healthy plant can fight off diseases and pests better than one that is overworked and tired.
By taking care of your plants, they will, in turn, take care of your environment. They can reduce indoor pollution and provide fresher air for you and your family to breathe. Hopefully this article answered, “Do plants sleep?”