All living things need water to stay alive,
and plants are living things! Plants, however,
need much more water than many living things
because plants use much more water than most
animals. Plants also contain more water than
animals - plants are about 90% water. The amount
of water a plant needs depends on the type of
plant, how much light the plant gets, and how
old the plant is. When plants are not watered
properly they wilt. This is because of something
called turgor, which is water pressure inside
the cells that make up the plant's skeleton.
Water enters a plant through its stem and
travels up to its leaves. When a plant is
properly hydrated, there is enough water
pressure to make the leaves strong and sturdy;
when a plant doesn't get enough water, the
pressure inside the stems and leaves drops and
Plants also need water for photosynthesis.
Photosynthesis is what plants do to create their
food, and water is critical to this process.
Water enters a plant's stem and travels up to
its leaves, which is where photosynthesis
actually takes place. Once in the leaves water
evaporates, as the plant exchanges water for
carbon dioxide. This process is called
transpiration, and it happens through tiny
openings in the plant's leaves, called stomata.
The water from the leaves evaporates through the
stomata, and carbon dioxide enters the stomata,
taking the water's place. Plants need this
carbon dioxide to make food. Transpiration -
this exchange of water for carbon dioxide - only
occurs during the day when there is sunlight.
This is why you might find dew on plants in the
morning. The plants contain a lot of water
because all night long water has been entering
through the stem and being pulled into the
leaves where it can't evaporate. Since the water
doesn't evaporate at night, the water has no
where to go so it remains on the leaves as
When water evaporates from a plant during
transpiration it cools the plant, in the same
way the humans sweat to cool off in the heat. A
mature house plant can transpire its body weight
daily. This means it gives off a lot of water!
If people needed that much water, an adult would
drink 20 gallons of water a day.
Actually, all living things need water
because life requires a LOT of chemical
reactions. The chemicals are usually dissolved
in water. Also, plants put the water together
with carbon dioxide to make sugar. This takes
energy, which plants get from light. Water also
helps plants stand up tall, even when they
aren’t made of wood. They don’t have bones, but
they do have cell walls and water pressure.
Water comes up from the roots, but carbon
dioxide doesn’t. How do you think plants get
Thanks for asking,
Plants need water for the same reason that
all living things do: to dissolve the chemicals
they use to do their biology. Plants also use a
water current up the plant for transport, which
evaporates water out the leaves, so they need
water for that reason, too. Lastly, water is
used to make sugar, and plants store energy in
the form of sugar.
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