^^ movement of water through the stem
TRANSCRIPT
Transport of Water and Minerals In
and Out of the PlantAnya Pena, Christian Solis, Jerick Bolintiam, Justine Alain Sy,
Noemi Nunez, Venus Banaag
Cell activities, such as diffusion, osmosis, imbibition, and guttation, involve the transport of water and materials
in and out of the cell membrane- which is essential for a plant to maintain equilibrium in an unstable environment.
The transport of the dissolved substances in different environments affects the plant cell in different ways. To
further understand the cell activities and the environment’s effect on the plant cell, seven different tests were
conducted. Diffusion of selected plant pigments was observed in the first experiment where Bixa orellana seeds
were placed in different test tubes containing different substances, namely: distilled water, boiled water, vegetable
oil, and heated vegetable oil. Osmosis was observed in the second experiment where small strips of the lower
epidermis of the Rhoeo spathodea was put two different slides- one with water and the other with salt solution. The
factors affecting the integrity of the cell membrane was determined in the third experiment using Pyrus Malus
peelings which was placed in different temperatures and substances. Imbibition was observed in the fourth
experiment where wood, rubber, and corn seeds were put in two beakers- one with water and the other with
kerosene. It was also noticed that each of the material had an increase in weight when placed in kerosene. The
movement of water through the stem was observed in the pechay stalk of the the fifth experiment. Transpiration was
observed in the sixth experiment which also compared four identical leaves with different applications of vasellin.
Finally, guttation was observed in rice seedlings which were covered with a wide mouth jar.
Keywords: diffusion, osmosis, cell membrane, imbibition, active transport, transpiration, guttation
The cell membrane is the biological
membrane separating the interior of a cell
from the outside environment. It is a semi-
permeable membrane surrounding all cells,
which controls the movement of substances
in an out of the cells; therefore, responsible
for maintaining a steady and stable living
condition—or a state of equilibrium—even
in the midst of a transient environment. It is
involved in a wide variety of cellular
processes, such as growth, absorption, and
respiration, and serves as the attachment
point for the intracellular cytoskeleton and,
sometimes, the extra-cellular cell wall.
There are two ways in which transport can
occur across a membrane, either by passive
or active, depending on the energy required
during the process. Simple diffusion, a kind
of passive transport, moves water from
regions of high water concentration (low
solute concentration) to regions of low water
concentration (high solute concentration).
This process however, is only possible for
solutes that are readily permeable such as
nonpolar and small polar molecules. Other
processes include: bulk flow, osmosis,
imbibition, and active transport.
Through this lab exercise, the student
should have been able: (1) To determine
some factors that affect the diffusion
process; (2) To differentiate between
diffusion and imbibition; (3) To determine
some factors that affect the permeability of
cell membranes; and (4) To demonstrate the
various processes by which materials are
transported and transpired.
METHODOLOGY
Diffusion of Selected Plant Pigments –
Atsuete (Bixa orellana) seeds were weighed
by Group number 1 and placed 1g of seed
was placed into 4 test tubes. These test tubes
were labelled 1-4. In test tube number 1,
10ml of distilled water was placed. In test
tube number 2, the group put 10ml of
distilled water and then placed it in a boiling
water bath. In test tube number 3, they put
10ml of vegetable oil. In test tube number 4,
10ml of pre-heated vegetable oil was placed.
After 30 minutes, these test tubes were
shook and the color intensities in each was
compared by using +, ++, and +++.
Osmosis – Thin sections of the lower
epidermal side of Bangka-bangkaan
(Tradescantia spathacea) were cut by Group
number 3 and these were placed into a wet
mount. Using this examination under the
LPO of the microscope, a sketch of a turgid
cell was made. Next, without moving the
slide, water was drawn off using a paper
towel and was replaced with a 5% salt
solution. A sketch showing the change in the
cells was then made based on the
observations under a microscope.
Factors Affecting the Integrity of Cell
Membranes – Apple peels were acquired by
our group by using a sharp blade. 7 sections
of peels were placed in a beaker filled with
distilled water. The first three sections were
transferred into three test tubes each with
10ml of distilled water and labelled A, B
and C. Test tube A was placed under room
temperature (250C) while Test tube B was
placed inside a refrigerator (100C) and Test
tube C was placed in a water bath (600 C).
After observing for 30 minutes, each of the
three sections were placed into wet mounts
and viewed under the microscope. Color
intensity in each was compared by using +,
++, and +++. For the remaining 4 sections,
they were also placed in wet mounts and
labelled D-G. A drop of pure chloroform
was added to D. A drop of 50% acetone was
added to E. 0.1 M of NaOH and 0.1 M of
HCl were added to F and G respectively.
These four were observed under the
microscope after 15 minutes and after 30
minutes. The observations were then
recorded.
Imbibition – The weights of 2 pieces of
wood and 2 pieces of rubber were weighed
by Group number 4. 2 sets of 10g corn seed
were also weighed. In one beaker, one piece
of wood, one piece of rubber and 10g of
corn seeds was placed. Water was added
until each of the materials was completely
immersed. In the other beaker, one piece of
wood, one piece of rubber and 10g of corn
seeds was and immersed with kerosene.
After 90 minutes, all the materials from the
two beakers were taken out and dried gently.
The final weights of these materials were
then measured.
Movement of Water Through the
Stem – Pechay leaves with intact petiole
were gathered by Group number 3. 1 cm
was cut off from the base of the petiole. The
leaves were immersed in a bottle filled with
10ml of 0.01% eosin dye solution. After 15
minutes, a leaf was removed and the stalk
was split longitudinally. The length covered
by the dye was measured. From another leaf,
a thin cross section of the stalk was cut and
viewed under the LPO of the microscope.
The stained tissues were then identified
through being viewed under the microscope.
Comparison of Cuticular and
Stomatal Transpiration by Four Leaves
Method – 4 identical leaves were gathered
by Group number 4. These were then
labelled A, B, C, and D. Leaf A was the
control. Using vasellin, each of the three
remaining leaves were greased. The upper
surface of B was greased while Leaf C had
its lower surface greased. Both sides of D
were greased. These leaves were then
hanged by a thread to expose both sides to
air. The set-ups were observed after one
meeting.
Guttation – 5 rice grains were planted
on a container by Group number 1. The
lower portion of the container was immersed
with water. When the seedlings are 2-5cm
long, they were covered with a transparent
bell jar (a wide-mouthed bottle can also be
used). This set-up was observed and the
droplets that formed on the leaf surfaces
were noted.
Results
Diffusion of Selected Plant Pigments –
The diffusion of the pigments of the seeds of
Bixa orellana is relatively faster and greater
in the setups exposed to higher
temperatures. Also, the diffusion was greater
in oil than in water, heated or not.
Substance ObservationTest Tube 1(Distilled Water)
+
Test Tube 2(Hot Distilled Water)
+++
Test Tube 3(Vegetable Oil)
++
Test Tube 4(Heated Vegetable Oil)
++++
Table 1. Shows the color intensity of the different setups, + being the lightest and ++++ being the
darkest Osmosis – To observe how the cell
changes in plasmolysis, wet mounts of
Tradescantia spathacea were made and the
water was later on replaced with a 5% salt
solution.
The cells were larger and turgid when it
was exposed in water (Fig. 1). When the
water was replaced with the 5% salt
solution, the cells became flaccid (Fig. 2).
Fig. 1 Tradescantia spathacea cells in a water solution
Fig. 2 Tradescantia spathacea cells in a 5% salt solution
Factors affecting integrity of cell
membrane – The results produced from this
experiment can be divided into three parts:
temperature, pH effects, and organic
solvents.
With temperature, the peeling of Pyrus
malus that was exposed to the lowest
temperature exhibited more damage to the
cell membrane while the one that was put in
a water bath exhibited less damage.
For organic solvents, the experiment
that pure chloroform is much more
damaging than 50% acetone.
As for pH effect, the one that was
subjected to NaOH, a base, had less damage
than the one subjected to HCl, an acid.
Fig 3.1 Pyrus malus soaked in water with a temperature of 10°C
Fig. 3.2 Pyrus malus soaked in water that has a temperature of 25°C
Fig. 3.3 Pyrus malus soaked in water that has a temperature of 60°C
.
Fig 4.1 Pyrus malus subjected to 50% acetone solution after 30 minutes
Fig 4.2 Pyrus malus subjected to pure chloroform after 30 minutes
Fig 5.1 Pyrus malus subjected to 0.1M NaOH solution after 30 minutes
Fig 5.2 Pyrus malus subjected to 0.1 HCl solution after 30 minutes
Imbibition – In this experiment, the
affinity of wood, rubber, and seeds to
different solvents, kerosene and water, were
compared. Wood and rubber makes good
imbibant of water as they showed greater
significant change in weight, while rubber
showed greater change in weight when it
imbibed kerosene.
Medium Imbibant Initial Weight(Wi)
Final Weight(Wf)
% Δ in Weight{(Wf-Wi)/Wi} * 100
Water rubber 0.5g 0.7g 40%wood 19.95g 21.6g 8.27%seeds 10g 12.1g 21%
Kerosene rubber 0.4g 0.7g 75%wood 16.9g 17.9g 5.92%seeds 10g 10.6g 6%
Table 2. Compares the affinity of certain plant materials to different solvents
Movement of water through the stem
– The 10mL of 0.01% of eosin dye solution
went up through the stem in a straight line
manner through the xylem tissues.
Fig. 6.1 Cross-section of pechay stalk
Fig. 6.2 External view of stained pechay
Comparison of cuticular and stomatal
transpiration by four leaves method –
Leaf A being the control, leaf B smeared
with grease and vaselin on the upper surface,
leaf C smeared with grease on the lower
surface, and leaf D smeared with grease on
the both sides, a week of observations were
made. Leaf A was the most desiccated one
and curled on both sides. Leaf B and C were
both half-dry with leaf B curling outward
and leaf C curling inward. Leaf D remained
fresh, waxy, and moist, with no occurrence
of desiccation and curling.
Guttation – The appearance of xylem
saps happened at the tip of the leaf blades
after the plant was covered with a wide
mouth jar.
DISCUSSION
Diffusion of selected plant pigments –
The greater the concentration gradient
between the outside and the inside of the
membrane, the greater the diffusion. If the
concentration of the pigments outside and
inside the membrane were greater, then it
would diffuse more quickly. The opposite is
also true. Another factor affecting the rate of
diffusion is the size of the particles. The
smaller the size of the particle, the faster it
would be diffused.
For the Bixa orellana seeds, the
carotenoids diffused more quickly when it
was submerged in the heated vegetable oil
solution. Generally, increases in temperature
speeds up the movement of molecules and
faster movements of molecules means faster
rates of diffusion. This is why the heated
distilled water and the heated vegetablle oil
had the fastest rates of diffusion.
As for the competition between oil and
water, faster rates of diffusion happened in
oil because the pigments of the Bixa
orellana seeds are insoluble in water.
Osmosis – When the Trandescantia
spathacea was immeresed in a hypotonic
solution, the cells became turgid. The water
was moving from a smaller concentration of
solutes than the solution on the other side of
the membrane. In a turgid cell, the water
will continually move into the cell until the
concetration of the impermeable solutes
equals to that of the hypotonic solution.
When the water was replaced with a
5% salt solution, the water bacame
hypertonic. The water then moved from a
larger concentration of solutes than the
solution on the other side of the membrane.
In a plasmolyzed cell, the water would
continually move out of the cell until the
concetration of the impermeable solutes
equals to that of the hypertonic solution.
Factors affecting the integrity of cell
membrane – In this experiment, the apple
peelings exhibited diffecrent intensities of
the color of their pigments. The darker ones
indicate more damage and stress to the cell
membrane while the lighter ones indicate
less stress and damage.
The ones with the damaged cell
membranes exhibited darker colors because
when the cell membrane gets destroyed, the
pigments from inside the cell leak out.
Temperature – 3 test tubes containing
immersed apple peelings in water were
subjected to different temperatures. In this
experiment, we have arrived with a
conclusion that lower temperatures inflict
more damage to the cell membrane and that
normal and high temperatures did not do
much damage.
pH effects – Wet mounts of 0.1M NaOH
solution and 0.1M HCl solution were
observed for 30 minutes. The results show
that the more acidic a solution is, the more
damage it can inflict to the cell membrane.
The more basic it is, the less damage.
Organic solvent – Chloroform inflicted
more damage in the membrane than the
acetone. In this one, the pH again got
involved. Chloroform is more acidic than
acetone.
Imbibition – Woods and seeds imbibed
better in water while rubber imbibed better
in kerosene. Water is composed of 2
molecules of hydrogen and a molecule of
oxygen, hence H20. Kerosene is an oil
distillate commonly used as a fuel or
solvent. It is a thin, clear liquid consisting of
a mixture of hydrocarbons and is primarily
derived from refined petroleum.
Imbibition occurs with or without the
help of living cells. According to Ferdinand
Sachs’ imbibition theory, water moves in
tubes in the walls of plants without the
cooperation of living cells and not within the
cell cavities.
There are no living cells in the veneer.
Veneer comes from the peeling of tree
trunks and these are secondary xylem, which
are dead cells.
Living cells are involved in the
imbibition of the seed. This is because the
entry of water takes place in the testa, which
may be actively dividing.
The swelling effect of imbibition in
seeds is important in seed germination
because imbibition in water can burst the
seed coat, which would signal the start of
germination.
Movement of water through the stem
– The 0.01% of eosin dye solution rose up
through the stem into the leaves. This only
shows that water moves through the xylem
elements in the stem to spread the water.
The eosin dye stain reached up to the
cross section of the leaf which means that
the water is diffused all throughout the plant
through the stem.
Comparison of the cuticular and
stomatal transpiration – Too much
transpiration can cause the dessication of the
leaves. Cuticle helps in preventing this. The
control set-up, leaf A, where nothing was
applied, desiccated while leaf D which was
smeared with grease on both sides remained
fresh and waxy without any occurrence of
desiccation.
Guttation – Since the jar was closed,
there was an excess of moisture in the
environment of the rice seedlings, hence, it
could not undergo transpiration, which why
guttation was induced.
Guttation is the release of water from
plants the hydathodes, which is induced by
root pressure, mainly because of the high
moisture content of the soil while
transpiration is the process of water vapor
loss from the internal atmosphere of the
plant.
Another difference is that in
transpiration, water vapor is released while
in guttation, xylem saps are released.
LITERATURE CITED
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