The Journey
of a Water
Drop
Bushra Shaikh 8C
What are the stages of the
water cycle?
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Evaporation/Evapotranspiration: When the water from the ground
evaporates to the atmosphere, evapotranspiration is when the water
from the plants evaporates from the leaves. These can be from vents,
volcanoes and fog.
Condensation: When the moisture from the ground makes contact with
the particles in the atmosphere to from water droplets.
Precipitation: The process when the droplets of water from the
atmosphere come down on earth in forms of rain, snow, sleet, hail etc.
Infiltration: The process where the water gets stored in places like
groundwater storage or can just escape from springs, seepage and
rivers.
What does the water do when
it gets into a plant?
There are three stages of which the water
goes through:
-
Root
Stem
Leaves
Root
First the water is collected through the piliferous region of the
root, this is where the youngest parts of the root hairs are. This
is a region that has a group of epidermal tissue projection to
increase surface area. This allows the plants maximum intake
of water. These hairs die off but are replaced by new growth
regularly. The water is absorbed through the epidermal tissue
through osmosis. A process where the water is moved from a
region of higher concentration to a region of lower
concentration. The concentration gradient indicates the
different in the concentration of solutes in a solution between
the two regions. To be more specific, “water molecules diffuse
too, but in living things water often diffuses across a
membrane.” (Schmoop, 2013)
Cohesion and Adhesion
So how does the water keep moving exactly? One of the characteristics of
water is water tension. This means that water has a bond, like a chain. So if
water is pulled through one end then the other end also comes along. So
when water transpires, (not evaporating because the water is going from a
living organism)and is drawn out the water throughout the rest of the plant is
pulled. This is the engine running the flow of water and this is why water
continuously moves throughout the plant. Cohesion and adhesion is where
we get into detail. Cohesion is a bond between to similar molecules whereas
adhesion is a bond between two different molecules. The hydrogen bonds in
the molecules (of the water) make them stick together (cohesion) and when
the hydrogen molecules form bonds with carbohydrates this forms adhesion.
The connection it has with this particular subject can be determined through
the cohesion tension theory. This theory says that when water is drawn out
through transpiration the water in the xylem is pulled towards it(adhesion).
The water flows consistently due to water tension and cohesion between the
hydrogen molecules present in water.
Stem
Next the water goes through the stem, the part that supports
the plant. There are two types of stems xylem and phloem. The
xylem is the vascular tissue of the plant. It distributes water and
dissolved minerals to all parts of the plant. The xylem also
contributes greatly in the replacement of water lost during
photosynthesis and transpiration. Sometimes the water moves
us due to root pressure capillary action. Root pressure occurs
due to too much water intake during low transpiration in the
plant. So if the root absorbs too much water form the moist soil
the water is pushed up because there is too much and some
of it needs to transpire. Furthermore, when the water increases
the sap in the xylem moves to the tip of the leaves and causes
guttation (when the sap forms drops on the tips of the leaves).
Leaves
The leaves help the water transpire. Transpiration occurs faster
during when there is more light or temperature. Subsequently the
heat motivates the stomata of the leaves to open more. The
stomata are miniscule pores on the outer layer of the leaf that
control the vapor passing in and out of the plant. Another reason
that the stomata are essential to plants because they also uptake
the gas needed for photosynthesis. Due to this stomata are mostly
open during the day, when photosynthesis occurs. Although,
there are certain types of plants called Crassulacean Acid
Metabolism which do photosynthesis at night! Therefore, their
stomata can also open at night! CAM plants are mostly desert
plants, like here in Qatar. Also, the drier and windier the
environment is the more transpiration occurs.
…
Furthermore (about leaves, in a diagram will appear to
have several different layers, each responsible for a
different job if not an interdependent one. After the
cuticle and the epidermis there is the palisade. The
palisade contributes mainly to photosynthesis and consists
of parenchyma cells. After this there is the mesophyll
(meaning leaf), most photosynthesis takes place in the
palisade mesophyll, which is efficiently located under the
epidermis at the top portion of the leaf. Different leaves
are adapted to their environments in different ways. There
may be leaves that are a different shape for example a
long leaf or a compound leaf. Sometimes there are even
leaves of different colors like red and pink!
Why does water need to
move consistently through a
plant?
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To keep the plant alive, continuously supplying it with
hydration and nutrients.
To keep the flow of the water going the water needs to
consistently be moving throughout the plant, if the plant
gets too much water it will rot and die.
Water is also incorporated into the cells, a percentage
of the cells are actually water.
Water is needed to activate photosynthesis, water helps
reacts with carbon dioxide to form the building blocks
needed for plant’s cell using the energy extracted from
the sunlight.
Bibliography
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"Adhesion and Cohesion of Water." Adhesion and Cohesion Water Properties, USGS Water Science
School. USGS, 2013. Web. 23 Mar. 2013.
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"The Water Cycle." , U.S. Geological Survey (USGS) Water Science School. USGS, 2013. Web. 23 Mar.
2013.
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Scully, Lizzy. "How Water Moves Through Plants." EHow. Demand Media, 15 Apr. 2009. Web. 23 Mar.
2013.
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Shmoop Editorial Team. "Transportation in the Plant - Shmoop Biology" Shmoop.com. Shmoop
University, Inc., 11 Nov. 2008. Web. 23 Mar. 2013.
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"Plant Water Regulation - Adaptation Tutorial." Plant Water Regulation. Biology-Online.org, 2013. Web.
23 Mar. 2013.
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"Concentration Gradient." - Definition from Biology-Online.org. Biology-Online.org, 2013. Web. 23 Mar.
2013.
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Shmoop Editorial Team. "Leaf Structure - Shmoop Biology" Shmoop.com. Shmoop University, Inc., 11
Nov. 2008. Web. 25 Mar. 2013.
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"Transport in Plants." Transport in Plants. N.p., n.d. Web. 25 Mar. 2013.