Plants consume oxygen at all times, not just at
night. Night is simply the time when the net
exchange of oxygen is into the plant; during the
day, when the plant can perform
photosynthesis, more oxygen is produced
than is consumed.
Plants need oxygen because plants are made
living cells which need to perform
cellular respiration to get the energy they need
Admittedly, needing to perform
cellular respiration alone does not mean
that consuming oxygen is required -
many (micro)organisms use fermentation or
anaerobic respiration. However, there are no
known anaerobic plants; all seem to need to
take in oxygen from the environment.
ScienceLine regarding plants
and their respiration.
Plants need energy in order to stay alive.
During the day, a plant can get its energy from
the sun, but it can't do that at night (unless
it's living in a lit up greenhouse, of course). To
get energy while in the dark, the plant must
consume its energy reserves, which are in
the form of sugar, and to extract energy from the
sugar, it must use the same oxygen-consuming
chemical reaction that you use when you get
energy from sugar.
Thus, no, there are no plants that don't
consume oxygen when it is dark. A plant that
is left in the dark without oxygen would
asphyxiate, for exactly the same reason that
an animal left without oxygen would asphyxiate.
The only difference between plants and animals is
that plants can get energy from light, and so
don't need oxygen when light is available.
We consume oxygen all day and all night, because
we breathe in oxygen and use it to 'burn' our
food. That's called 'aerobic respiration.'
Without oxygen, you can only burn food part way,
and you don't get so much energy from the food -
that's called 'anaerobic respiration' and it
happens in our muscles when we exercise hard.
'Aerobic' is 'with air.' You can find that stuff
It's stressful for plants not to have enough
oxygen. Scientists are figuring out the ways
plants get energy when they don't have enough
oxygen. When plant seeds get flooded with too
much water, they can live for a while, but then
they will die.
Plants, like animals, undergo cellular
respiration to break down food (in the form of
sugar, or glucose,
energy to live. Respiration requires oxygen
to convert the glucose into energy, water, and
carbon dioxide. And in fact, plants undergo
respiration all the time, both night and day.
You may be familiar with photosynthesis,
where plants use carbon dioxide (CO2)
from the air, water, and sunlight to create food
(again glucose or sugar) and oxygen. But you may
not have realized that photosynthesis is really
only happening in the green parts of the plant. So
while the leaves and stems are producing oxygen
during photosynthesis, meaning those cells have
available oxygen for respiration, the parts of
plants that do not undergo photosynthesis (such as
roots), need oxygen for respiration. Thus all
plants require oxygen to survive because all
plants require respiration to live, and thus there
are no examples of plants that do not need
In continuation, I suspect you have heard that
there are organisms that don't require oxygen to
live, and that might prompt you to think there
could also be plants that don't require oxygen.
What would be more accurate is to say that all
plants and animals need oxygen to live, but
some microorganisms don't require oxygen to
live. You can think of this from an evolution
perspective. Earth's atmosphere was not always
rich in oxygen and the organisms were
anaerobic, meaning oxygen was not required
for growth (and in fact oxygen was deadly to these
organisms). Then about 2.5 billion years ago, a
certain type of cyanobacteria evolved the ability
for oxygen photosynthesis. These cyanobacteria
started producing oxygen gas which in turn
increased the oxygen in the atmosphere. The
presence of oxygen caused most of life at the time
to die from the toxicity of the newly oxygen-rich
environment. This time in Earth's history is often
called the Great Oxygenation Event (GOE),
and the remaining life after extinction only
survived by adapting the ability to live in an
Plants and animals today come from the
survivors that developed oxygenic respiration.
Therefore, the only organisms today that can live
without oxygen are thought to represent those
early, simple structured organisms before the
That said, scientists are always finding new
discoveries. There is a group of tiny
marine-sediment dwellers that are considered
animals that do not require oxygen to survive. But
these complex organisms evolved in an entirely
oxygen-free environment, so if there are plants
that do not require oxygen, scientists have not
found them yet.
Click Here to return to the search form.