Why do plants need oxygen through their roots?

Why do plants need oxygen through their roots?

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I was asking myself why plants die from over-watering and the simple answer was that they can't get enough oxygen through their roots. But this made me ask myself why they need oxygen in their roots since oxygen is a product of photosynthesis and plants even release oxygen through their leaves.

With this seeming surplus of oxygen, how can plants "suffocate" when their roots dont get enough oxygen from the soil?

Plants need oxygen but don't have a heart

Complex animals all have a circulatory system of some sort to get oxygen throughout the body for respiration. Plants also do respiration even though they are net producers of oxygen through photosynthesis.

Plants also have a bit of a circulatory system, but for the most part it isn't nearly efficient enough to deliver oxygen everywhere in the plant: plants don't have anything like circulating hemoglobin-filled cells we are familiar with in vertebrates, and although fluids flow in plant circulatory systems, they aren't circulating quickly like you are familiar with in your own body. This means that plants need to get oxygen near to where it is needed.

Roots, in particular, consume oxygen

The problem of a plant not getting enough oxygen through its roots isn't because the whole plant gets oxygen through the roots, it's because the roots themselves need oxygen to function. Roots do a lot of 'heavy lifting' in a plant, literally: they are pumping ions across membranes to pull in water, to concentrate other nutrients that the plant needs for survival and growth, and to pressurize the plant enough for those nutrients to make it up into the leaves. Those processes take energy, and in turn they need oxygen.

Additionally, photosynthesis isn't taking place in the vicinity of the roots: plants are both taking in CO2 and releasing oxygen from their stomata in the leaves and stems.

If roots cannot get enough oxygen, for example due to overwatering, the roots themselves are damaged, and this harms the plant as a whole.


Because there are always exceptions in biology, it should be noted that some plants are indeed adapted to wet environments and have better systems for promoting the diffusion of oxygen including increasing the amount of air space in the roots, where oxygen diffuses more quickly than through aqueous media. Other plants use fermentation in their roots to survive temporary hypoxia.


Colmer, T. D. (2003). Long‐distance transport of gases in plants: a perspective on internal aeration and radial oxygen loss from roots. Plant, Cell & Environment, 26(1), 17-36.

Drew, M. C. (1992). Soil aeration and plant root metabolism. Soil Science, 154(4), 259-268.

Justin, S. H. F. W., & Armstrong, W. (1987). The anatomical characteristics of roots and plant response to soil flooding. New Phytologist, 106(3), 465-495.

Laan, P., Tosserams, M., Blom, C. W. P. M., & Veen, B. W. (1990). Internal oxygen transport inRumex species and its significance for respiration under hypoxic conditions. Plant and Soil, 122(1), 39-46.

Plants are living things. And living things need oxygen to survive. While plants may produce oxygen as a byproduct during photosynthesis, they still require to undergo respiration, which requires oxygen.

Can Photosynthesis Occur Without Oxygen?

Photosynthetic reactions can occur without oxygen that is anoxygenic thus, they do not produce oxygen. There is a process called Phototrophy by which organisms trap light energy or photons to store it as chemical energy in the form of ATP or adenosine triphosphate and/or reducing power in NADPH.

Two major types of phototrophy are – chlorophyll-based chlorophototrophy and rhodopsin-based retinalophototrophy. Chlorophototrophy can further be divided into i) oxygenic photosynthesis and ii) anoxygenic phototrophy. These Oxygenic and anoxygenic photosynthesizing organisms undergo different reactions either in the presence of light called “light reactions” or with no direct contribution of light to the chemical reaction called “dark reactions.”

Anoxygenic photosynthesis is the phototrophic process that captures and converts light energy to ATP, without producing the oxygen and water is not used as an electron donor.

There are several groups of bacteria that undergo anoxygenic photosynthesis:

  • Green sulfur bacteria
  • Green and red filamentous anoxygenic phototrophs (FAPs)
  • Phototrophic purple bacteria
  • Phototrophic Acidobacteria
  • Phototrophic heliobacteria.

Anoxygenic phototrophs have photosynthetic pigments called bacteriochlorophylls, which are similar to chlorophyll found in eukaryotes. Bacteriochlorophyll a and b have wavelengths of maximum absorption at 775 nm and 790 nm, respectively, in ether.

The Chemical Composition of Plants

Since plants require nutrients in the form of elements such as carbon and potassium, it is important to understand the chemical composition of plants. The majority of volume in a plant cell is water it typically comprises 80 to 90 percent of the plant&rsquos total weight. Soil is the water source for land plants, and can be an abundant source of water, even if it appears dry. Plant roots absorb water from the soil through root hairs and transport it up to the leaves through the xylem. As water vapor is lost from the leaves, the process of transpiration and the polarity of water molecules (which enables them to form hydrogen bonds) draws more water from the roots up through the plant to the leaves (Figure (PageIndex<1>)). Plants need water to support cell structure, for metabolic functions, to carry nutrients, and for photosynthesis.

Figure (PageIndex<1>): Water is absorbed through the root hairs and moves up the xylem to the leaves.

Plant cells need essential substances, collectively called nutrients, to sustain life. Plant nutrients may be composed of either organic or inorganic compounds. An organic compound is a chemical compound that contains carbon, such as carbon dioxide obtained from the atmosphere. Carbon that was obtained from atmospheric CO2 composes the majority of the dry mass within most plants. An inorganic compound does not contain carbon and is not part of, or produced by, a living organism. Inorganic substances, which form the majority of the soil solution, are commonly called minerals: those required by plants include nitrogen (N) and potassium (K) for structure and regulation.

Roots and Worms Science Lesson

All About Earthworms

Earthworms live in the soil of every continent in the world except for Antarctica! There are about 2700 different kinds of them.

They aren’t much to look at (they may even seem a little gross), but earthworms are really good at what they do. You might be surprised to learn that their job is a very important one. So, what do they do? They dig tunnels through soil in the ground. As they go, they eat, digest their food, and then excrete it. That doesn’t sound very important. Well, it turns out, the “waste” that worms excrete is actually very valuable for soil. It is full of nutrients that help plants grow. The tunnels they form also help keep the soil healthy by supplying it with oxygen and making it easier for water to soak into the ground. Worms periodically come up to the surface of the ground to find food, then go back down and continue tunneling. This process helps mix up the richer soil from farther down in the earth with the soil at the top. This is important because lots of the nutrients in topsoil have already been used up by plants and the soil down below has more nutrients. All of these things make the soil better for plants to grow in. This is important for us since most of our food comes from plants or from animals that eat plants.

Earthworms are excellent recyclers! They eat things like fallen leaves and decaying animals. They can also eat food scraps, fruit and vegetable peels, eggshells, and some garbage (like coffee grounds and tea bags). Organic matter – something that came from a living thing, such as a plant or animal – will break down on its own eventually, but an earthworm can eat and digest an amount of food and dirt equal to its own weight in a single day, so the process goes much faster with their help! This keeps the soil full of helpful nutrients.

Worms need food, oxygen, and moisture to live. They breathe through their skin instead of with lungs. Oxygen from water in the ground can pass through a worm’s skin to keep it alive. They like the soil to be damp so that their skin can stay moist and slimy, but not too wet. If you go outside after a rainstorm, you might be able to spot some earthworms on the sidewalk. Sometimes after heavy rain, earthworms come up to the surface because they’ve gotten too much water while in the ground. UV rays from sunlight can kill worms very quickly, though, so if the rain storm happens during the day and the sun starts shining again, earthworms that have come up to the surface often get burned by the sun’s rays and die. If you happen to see any earthworms on the sidewalk, it’s a good idea to use a stick to move them back to an area with dirt.

Anatomy of an Earthworm

Earthworms are very simple creatures. They don’t have arms, legs, or ears. Instead of eyes, they have special cells on the outsides of their body that are very sensitive to light. Those cells help them see light, but nothing else. They have small simple brains that are used to help them move their bodies. They can also have up to five hearts to help pump blood through their long bodies.

An earthworm’s body is divided into lots of segments and they have a head end and a hind end. The very first of the tiny segments is the earthworm’s mouth and the last segment is its anus, where waste, called castings, exits its body. Both ends look similar, but you can tell the head end by the thick ring-like segment that is located near it.

An earthworm’s mouth is very small, but it is strong enough that it can hold onto a leaf and drag it around as the worm moves! When an earthworm eats, it uses a muscle in its throat to move the food down into a little space called a crop. The food stays in the crop for a little while, sort of how food stays in your stomach for awhile. Then it is pushed into another space called a gizzard. The gizzard has large grains of sand and small stones in it from the sand and dirt the worm has eaten. To digest the food, the gizzard squeezes in and out and the sand and stones rub together and grind up the food! From there it passes through the worms intestines where the worm gets all the nutrition it needs from the food. Then it exits the worm’s body as castings.

All About Roots

Most plants start their life as some sort of seed. A seed has all of the information it needs to grow into a plant, but before it can grow, it needs certain conditions to be right. When it has everything it needs (warmth, oxygen, and water), it will sprout. The sprouted seed will soon grow a stem above the ground. Below the ground, it will grow roots. The roots grow downwards into the soil. Roots are very important for plants. They help hold the plant in place in the soil while it grows. They also provide water and nutrients that the plant can’t live without. The roots soak up nutrients and water from soil, then the nutrients move up the roots into the stem of the plant to reach the leaves, flowers, and fruit. Roots have tiny hairs on them to help absorb water and nutrients from the soil. Sometimes plants use their roots to store extra food, especially during the winter.

Do you remember what plants need in order to grow? They need sunlight, air, and water. They also need nutrients. The best way for plants to get nutrients is from soil. As you’ve already learned, earthworms help provide soil with lots of great nutrients. A plant’s roots are the parts that allow a plant to use the nutrients that the worms provide. Roots help plants grow, and then earthworms eat the leftover parts of plants and the cycle starts all over again!

There are several different kinds of roots. Some plants have many roots and some just have a few. Trees have large systems of roots – some really big ones to help hold the tree up safely in the ground, and lots of smaller ones to help the tree get water and nutrients. Some vegetables, like carrots, radishes, and turnips, are actually roots! They are called taproots, because they just have one long main root. Sugar comes from a type of root, called a sugar beet, which is similar to a root vegetable.

Besides keeping a plant in place, roots can help keep soil in place. For example, the roots from trees growing along the edge of a river or near an ocean can help hold the soil in place when water washes over it.

Printable Worksheet

This worksheet can be used as either a matching game (by cutting out all eight root and plant pictures) or as a cut-and-paste review of different roots that plants can have. Take a moment to discuss how different kinds of plants use their different types of roots and why they might be shaped the way they are.

Carbon-Oxygen Cycle

Carbon and oxygen are independent of each other, but are very closely connected as well as interdependent on each other. The following article will cover information that will help you understand the carbon-oxygen cycle in detail.

Carbon and oxygen are independent of each other, but are very closely connected as well as interdependent on each other. The following article will cover information that will help you understand the carbon-oxygen cycle in detail.

Life on planet Earth continues due to the presence of organic as well as inorganic nutrients present in the nature. It is very important for these nutrients to be continuously recycled. If this doesn’t happen, all the nutritive resources in the world will get extinguished completely. No nutrients means no life on Earth. So, in order for the life cycle of every living being, unicellular or multicellular organism to sustain, recycling of the nutrients is very important. One of the important cycles is the carbon-oxygen cycle.

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The Process of Carbon-Oxygen Cycle

There are four steps involved in the completion of this cycle. These methods are discussed below:

Plants undergo photosynthesis that helps them produce energy and food for themselves. During this process, plants take in carbon dioxide (CO2) and absorb water (H2O) with the help of their roots. The chlorophyll present in the leaves and the energy from the sun, helps convert CO2 and H2O into Oxygen O2, sugar and water vapor. Oxygen (O2) is released by the plants as a by-product into the atmosphere.

The carbon dioxide from air and water from the soil in presence of light (energy) is taken by the plants and converted into carbohydrates and oxygen as by-products.

Just as plants carry out photosynthesis, animals carry out respiration. Respiration occurs when animals take in oxygen from the air along with simple sugars from their food. This helps in release of carbon dioxide, water and energy from the animal body. During cellular respiration, animals require O2 while inhalation. When they exhale the waste product of cellular respiration, they release CO2 into the atmosphere again.

Formula for Respiration

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The carbohydrates taken from food like plants or carbon-based compounds along with oxygen are converted to carbon dioxide which is released into the air along with water and energy during respiration.

It is a process of burning that occurs naturally in the nature. For example, volcanic eruptions are natural combustion processes where carbon dioxide is released into the atmosphere due to burning. Nowadays, there are many environmental pollutants that cause an increase in the amount of CO2 in the air. These include cars, factories, burning of woods, coals, nuclear energy, gas, etc. This irresponsible combustion and release of excessive carbon dioxide and other harmful gases in the environment is the major contributing factor for today’s global warming.

After the death of any living organism, i.e., unicellular or multicellular organism, it gets decomposed. This decomposition means insects, fungi and bacteria (together called decomposers), help in breaking down the cellular components of the dead organism into its basic elements. These elements include water, calcium, nitrogen, carbon and oxygen. Thus, decomposers help in release of oxygen and carbon dioxide back into the atmosphere as their metabolic waste products.

The entire cycle can be summarized as, plants taking in carbon dioxide and releasing oxygen during photosynthesis. This oxygen released is taken up by animals who release carbon dioxide after carrying out respiration. Thus, the recycling of carbon and oxygen in the atmosphere will continue as long as respiration and photosynthesis occur. This also proves that, to sustain life, plants are very important as they are the major contributors to the amount of oxygen present in the atmosphere. Although both cycles occur independently, they are, in a small way, interconnected to each other.

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Why can't the ringing experiment be performed in monocotyledon plants?

Who established the ringing experiment & why can't the experiment be performed in monocotyledon plants?"

The Ringing Experiment

The ringing experiment involves removing a selected part of a stem tissue in the form of a ring or a girdle. There are two types of ring tissues removed one the phloem is removed only and the second one, the xylem is removed. Three plants are selected in the ringing experiment. The three selected plants are kept under sunlight to allow photosynthesis take place. Let the plants be Plant A, B, and C. After a short duration of sunshine, it is noticed that in plant B, the portion of the cut stem immediately bulges above the ring. On the other hand, plants A and C have no any sign of bulging. This works on the foundations of downward translocation taking place in the phloem as plant's B phloem was removed. Such instances didn't happen in plants A or C as the phloem was still intact. This suggests that the removal of xylem had no effect on the translocation as seen in A.

In the next experiment, a similar procedure will be followed showing the upward translocation also conducted through the phloem. The procedure starts with the removal of the xylem in Plant A, removal of phloem in plant B and control in plant C. The shoots in A and B are defoliated above the rings. The cut part is kept in glass cylinder which is filled with water so as to keep the tissues moist. In plant A, where only the xylem was removed shows the stem elongation. This shows that there was an undisturbed movement of solutes through the phloem. In plant B, there is no elongation seen. This indicates that the stoppage of solute flow in the stem was removed.

Tracer studies with the sap analysis which clearly shows that sieve tubes are the main structures in which organic materials translocate within the plant. This is the method used to determine translocation in plants. In tracer experiment, the main aim is to know the flow of sucrose. This procedure utilizes radioactive carbon dioxide where C is treated as 14C. Carbon dioxide which simply means in CO2 there is only one carbon and two oxygen atoms. The radioactive carbon dioxide is placed in a bag over the experimenting leaf and sealed. After a while, the carbon dioxide will be converted into glucose form where an X-ray is taken so as to show where the radioactive material has moved clearly.

Another experiment procedure is where a plant is grown in a lab and one leaf exposed to a carbon dioxide which contains radioactive isotope 14C. This 14CO2 is taken up by the plant during photosynthesis, and then the 14C is incorporated into sucrose and glucose. Later on, the plant gets frozen into liquid nitrogen so as to kill and fix it fast enough and then placed on a photographic film in the dark. The results show an autoradiograph outlining the compound location containing the 14C. The experiment shows how organic compounds are transported downwards from the leaves to the roots in a plant. The technique can be used to trace the ions, sugars or water.

Explain how organic substances are translocated in plants?

Mass flow, simply put, is the movement of matter of one substance through a designated channel. In plant physiology, this often includes the upward movement of water in the soil into vascular plant tissue. The general movement of materials from exchange surfaces to the necessary cells through the plants mass transport system is accomplished by mass flow.

What are the scientific methods to investigate transport in tracer and ringer experiments?

I have to write an essay answering this question but I am not able to find enough information to complete the essay.

The scientific method is a process used by scientists and researchers to carry our experiments and research. The scientific method includes several steps:

    Ask a question or create a question you would like to answer with your experiment.

Animals have to find and eat food, but plants are able to make their own by using sunlight energy. This process, called photosynthesis, provides plants with the energy and raw materials for growth.


The leaves of plants trap sunlight energy, which changes carbon dioxide gas and water into an energy-rich food called glucose. Glucose provides the plant with energy, and is also used to make substances such as cellulose, which forms the plant?s cell walls.

STEMvisions Blog

When you get hungry, you grab a snack from your fridge or pantry. But what can plants do when they get hungry? You are probably aware that plants need sunlight, water, and a home (like soil) to grow, but where do they get their food? They make it themselves!

Plants are called autotrophs because they can use energy from light to synthesize, or make, their own food source. Many people believe they are “feeding” a plant when they put it in soil, water it, or place it outside in the Sun, but none of these things are considered food. Rather, plants use sunlight, water, and the gases in the air to make glucose, which is a form of sugar that plants need to survive. This process is called photosynthesis and is performed by all plants, algae, and even some microorganisms. To perform photosynthesis, plants need three things: carbon dioxide, water, and sunlight.

By taking in water (H2O) through the roots, carbon dioxide (CO2) from the air, and light energy from the Sun, plants can perform photosynthesis to make glucose (sugars) and oxygen (O2). CREDIT: mapichai/

Just like you, plants need to take in gases in order to live. Animals take in gases through a process called respiration. During the respiration process, animals inhale all of the gases in the atmosphere, but the only gas that is retained and not immediately exhaled is oxygen. Plants, however, take in and use carbon dioxide gas
for photosynthesis. Carbon dioxide enters through tiny holes in a plant’s leaves, flowers, branches, stems, and roots. Plants also require water to make their food. Depending on the environment, a plant’s access to water will vary. For example, desert plants, like a cactus, have less available water than a lilypad in a pond, but every photosynthetic organism has some sort of adaptation, or special structure, designed to collect water. For most plants, roots are responsible for absorbing water.

The last requirement for photosynthesis is an important one because it provides the energy to make sugar. How does a plant take carbon dioxide and water molecules and make a food molecule? The Sun! The energy from light causes a chemical reaction that breaks down the molecules of carbon dioxide and water and reorganizes them to make the sugar (glucose) and oxygen gas. After the sugar is produced, it is then broken down by the mitochondria into energy that can be used for growth and repair. The oxygen that is produced is released from the same tiny holes through which the carbon dioxide entered. Even the oxygen that is released serves another purpose. Other organisms, such as animals, use oxygen to aid in their survival.

If we were to write a formula for photosynthesis, it would look like this:

The whole process of photosynthesis is a transfer of energy from the Sun to a plant. In each sugar molecule created, there is a little bit of the energy from the Sun, which the plant can either use or store for later.

Imagine a pea plant. If that pea plant is forming new pods, it requires a large amount of sugar energy to grow larger. This is similar to how you eat food to grow taller and stronger. But rather than going to the store and buying groceries, the pea plant will use sunlight to obtain the energy to build sugar. When the pea pods
are fully grown, the plant may no longer need as much sugar and will store it in its cells. A hungry rabbit comes along and decides to eat some of the plant, which provides the energy that allows the rabbit to hop back to its home. Where did the rabbit’s energy come from? Consider the process of photosynthesis. With the help of carbon dioxide and water, the pea pod used the energy from sunlight to construct the sugar molecules. When the rabbit ate the pea pod, it indirectly received energy from sunlight, which was stored in the sugar molecules in the plant.

We can thank photosynthesis for bread! Wheat grains, like the ones pictured, are grown in huge fields. When they are harvested, they are ground into a powder that we might recognize as flour. CREDIT: Elena Schweitzer/

Humans, other animals, fungi, and some microorganisms cannot make food in their own bodies like autotrophs, but they still rely on photosynthesis. Through the transfer of energy from the Sun to plants, plants build sugars that humans consume to drive our daily activities. Even when we eat things like chicken or fish, we are transferring energy from the Sun into our bodies because, at some point, one organism consumed a photosynthetic organism (e.g., the fish ate algae). So the next time you grab a snack to replenish your energy, thank the Sun for it!

This is an excerpt from the Structure and Function unit of our curriculum product line, Science and Technology Concepts TM (STC). Please visit our publisher, Carolina Biological, to learn more.

[BONUS FOR TEACHERS] Watch "Photosynthesis: Blinded by the Light" to explore student misconceptions about matter and energy in photosynthesis and strategies for eliciting student ideas to address or build on them.

The Opposite Of Photosynthesis

Here's a more detailed explanation of the process of respiration in plants. We already mentioned how it involves using the glucose (sugars) that is produced during photosynthesis in combination with oxygen to create energy. This energy is responsible for the growth of plants. Respiration can be considered the opposite process of photosynthesis. Plants produce their food in the natural world.

Respiration can be considered the opposite process of photosynthesis.

Plants use carbon dioxide from the environment and produce glucose and oxygen. These can later be used as an energy source. Photosynthesis only takes place in the leaves and stems. This is different from the process of respiration. It occurs in the roots, as well as the leaves and stems. Plants get the oxygen needed for this process through the stomata. The process of respiration takes place in the mitochondria of the cells once oxygen is present. This process is called aerobic respiration.


As a fringe benefit, if we can grow food in space, this is likely to lead to a happier crew. We aren't machines, and most human beings enjoy having plants around and growing plants.

First, there's the taste. Fresh food, lettuce leaves and tomatoes picked from the plant, and bread you bake yourself, from wheat you grew yourself tastes much better than food that is dried and reconstituted, which is all you'd have otherwise in a long duration journey.

Also most people enjoy having plants around and tending plants.

It's true that you can survive fine without plants. If you are a prisoner in solitary confinement, you have no choice, and may find that you adjust fine to your situation. And many hermits in the past, and even today, spend years on end in caves and other confined small places, without any plants or much of anything except blank walls, and come out of their retreats happy. It is the same also for the crew of rowing boats and such like on long distance voyages, for instance when rowing across the Pacific, they live in confined quarters for weeks or months on end, and are happy in those situations.

However, that's not for everyone. Having plants around in the spaceship, and fresh food that they have grown themselves seems likely to contribute to overall happiness and well being of the crew. This is often mentioned as a fringe benefit in the literature. And in a small way, this has already happened - in the ISS tending their small crop of plants has a calming effect on the astronauts and cosmonauts.

A happy crew will make better decisions, and are more likely to come up with inspired and creative solutions to problems, and so may be better at completing mission objectives. And in any case, all things being equal, surely it's better to go for a solution that is more enjoyable for the crew.

Especially on long duration missions, far from Earth, where their plants in their spaceship may be the only green thing there is for many light minutes, many millions of kilometers, in all directions. Even on the far side of the Moon, the green plants in their spaceship may be their one direct tangible link with the ecosystem of the Earth which they can no longer see in the sky.