Most people know a little about what it takes to grow a plant. A good light source is considered almost essential. But does that mean the plant stops growing when the sun goes down? What happens to the energy created during the day? Do plants grow at night?
Do plants grow at night? Yes! The absence of light actually encourages plants to grow faster at night. Phytochromes in plants sense darkness, stimulate the production of growth hormones, and cause the plant to elongate in search of light. The same process helps plants orient their foliage toward light and helps seedlings stretch for light.
Read on to learn more about what your plants do at night!
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Do plants grow at night?
Let’s start with what we know: plants use sunlight for photosynthesis. When sunlight hits leaves, it activates tiny chloroplasts in plant cells. The chlorophyll in the chloroplasts of cells acts almost like miniature solar panels, collecting and storing energy from the sun.
They use this energy to convert carbon dioxide and water into glucose and oxygen. The oxygen ends up in the air as a waste product, while the remaining energy-rich glucose can be used for nutrition and growth or stored in roots, leaves or fruits for later use.
Plants take advantage of sunlight during the day and produce as much food as possible and store the excess. Photosynthesis therefore continues as long as there is sufficient water and light available.
There are many other things that happen during photosynthesis that I won’t go into, but this explanation is enough to understand what happens to plant growth after the sun goes down.
Plants don’t sleep, which means they don’t go to sleep at night. When the sun goes down or the lights go out, plants cannot continue photosynthesis, but they can continue to breathe, the process by which living organisms convert nutrients into energy for biological functions and growth.
What is Breathing?
Respiration allows a plant to use the glucose it has produced through photosynthesis. Oxygen and glucose are used for respiration, producing carbon dioxide and water and releasing energy in the process.
One crucial thing to keep in mind is that plants use oxygen all the time, day and night, to breathe, and they use energy for their essential functions and growth. Most people think plants don’t use oxygen during the day, but that’s not true. The reality is that plants use more carbon dioxide than oxygen during the day and more oxygen than carbon dioxide at night. In general, plants are producers of oxygen and consumers of carbon dioxide.
Why does a plant need to breathe?
The movement and reuse of the resources produced by photosynthesis are necessary for the growth of new cells and therefore new leaves, stems and roots. For plants to grow, they are stronger, they need to eat, just like humans.
Getting all that food where it needs to go isn’t the whole story. Believe it or not, plants have a pretty remarkable growth spurt just before sunrise, as any time-lapse photographer can tell you. This growth spurt comes down to an idea called rhythmic plant growth, which is similar to the circadian rhythm that humans experience.
For those unfamiliar with this concept, it occurs when the hypothalamus in the brain responds to signals that pass through our optic nerves at night. These signals tell the hypothalamus that it is dark outside, so it must be night and time to rest. Your brain responds by producing melatonin from the pineal gland to lull you to sleep.
Your circadian rhythm tends to coincide with the natural cycle of day and night, creating a natural routine for sleeping at night and being alert during the day. Believe it or not, a routine like this can be seen in humans and plants.
plant growth spurts
Do plants grow at night? Not only do they grow, but their growth is supercharged!
A team of biologists from the Instituto Salk de Estudios BiológicosUC San Diego y la Universidad Estatal de Oregón querían demonstrate that the plantas crecen más rápido justo antes del amanecer y que este crecimiento se produce en rachs que superan con creces la tasa de crecimiento en otros momentos of the day.
They wanted to achieve this by trying to understand how hormone biosynthesis correlates with the rhythmic growth of plants.
To do this, they first looked at the plants’ phytochromes, which detect how much shade the plant receives. If the plant is too shaded, growth hormones are sent to elongate the shaded part of the plant, increasing the chances that the plant will receive more sun.
If you’ve ever left something on your lawn, you may have noticed that the grass around it grew longer than the other grass. If you thought your garden was fighting you, you’re right. This process is essential for the survival of plants, but what causes them to be released?
Scientists have found that the genes needed to release these growth hormones just before sunrise share a common DNA sequence. They called this main controller the HUD element which stands for “Dawn Hormone”.
It controls the gates that release growth hormones, opening them at just the right time to flood the edges and kick-start that growth spurt before sunrise and closing the gates until the next 24 hour cycle is complete. They also believe that the HUD element has a protein that binds to regulate its function, but this remains a mystery.
Long day plants vs. short day
If you’ve ever seen plants classified as short-day or long-day, it’s because of what happens to the plant at night. This classification is determined by the photoperiodism or the amount of light or darkness a plant needs to grow.
Daylength was once thought to be the crucial factor in this process, hence the terminology. In fact, as later discovered, it is the duration of darkness that is crucial for initiating flowering in both long-day and short-day plants.
Short-day plants need more than 12 hours of darkness to flower for several weeks. They bloom in winter or spring as this coincides with shorter days and longer nights.
If you’ve ever tried to rebloom a poinsettia or kalanchoe without success, it’s probably because they need long periods of long nights to kick-start the flowering process.
Long-day plants need less than 12 hours of darkness to flower. They bloom in summer when the days are long. Many summer-blooming vegetables and flowers are long-day plants, so we enjoy their blooms during the long summer days.
Some plants are not affected by day length. These are called day neutral plants. Some examples are cucumbers, tomatoes and corn.
Short-day and long-day plants are divided into quantitative and qualitative plants. These plants need a certain amount of sunlight or darkness to stimulate a certain response. Poinsettias, for example, need a certain amount of darkness to turn red. In other words, they need less sun to acquire a certain quality that makes them a quality plant.
Rye is an example of a quantitative plant. It produces seeds regardless of how many hours of sunshine or darkness it is exposed to, but it produces more seeds when it receives more sunlight. Sun exposure determines how much of it you produce.
How much darkness do plants need?
It depends on the plant. As mentioned, some long-day plants need a lot of sun, while short-day plants don’t. Some examples of long-day plants include the most common vegetables and herbs, especially spinach and dill, as well as ryegrass, clover, asters, hibiscus, and carnations.
On the other hand, short-day plants include chrysanthemums, daisies, soybeans, onions, cotton, violets, rice, sugarcane, and poinsettias.
What about indoor plants?
When thinking about your houseplants and the amount of light and dark periods, in most cases it’s best to choose a plant that can tolerate a bit more darkness.
Indoor plants rarely receive the same amount of light as outdoor plants. Most long-day plants need at least 12 hours of sunlight, which is very difficult for a houseplant to provide.
When it comes to indoor plants, the best way to determine which type to get is to assess the amount of light your home receives in the area where you plan to place a plant. Consider how many windows you have and whether the windows face north, south, east or west. Due to the nature of houseplants, it’s best to think about how much light you can give them. Darkness is usually not a problem.
What about artificial light and indoor plants?
Even in conditions where houseplants receive little natural light, they still need darkness to ensure a healthy growth pattern. That said, you may want to consider the amount of artificial light your plants receive.
Plants do well in natural light, but artificial light can make a big difference to a plant that isn’t optimally lit. Although you have complete control over this type of exposure, some people don’t give it much thought. If you have houseplants, don’t leave artificial lights on all the time, as this can cause major problems with growth, flowering and bud development.
Don’t worry if you forgot to turn off the light once or twice before going to bed. An occasional night or two is unlikely to have any long-term effect on the health of your houseplant. That said, having the lights on all the time affects your plants in a number of ways.
Besides preventing it from getting the hours of darkness it needs to thrive, too much light also increases the heat in and around the plant, causing it to dry out and ultimately kill the plant.
So if you’re asked if plants grow at night, share this interesting aspect of plant biology.