Transcript
Measurement of Osmotic Potential () by Incipisnt Plasmolysis
GROUP III
Yunandar/1114040181Surhayanti Amir/1114040192
Sri Vianita/1114040195Sri Wahyuningsih/1114040199
BIOLOGY ICP
UNIVERSITAS NEGERI MAKASSAR TAHUN AJAR 2012/2013
CHAPTER IINTRODUCTION
A. Background
Water potential (Ψw, psi), which is a measure of the energy state of water
is affected by dissolved solutes, pressure and matrix particles. The contribution to
water potential by dissolved solutes, termed osmotic potential (Ψs ), is always
negative in sign. In other words, solutes decrease the water potential. The
contribution of pressure (Ψp) may be positive, negative or zero, but is generally
positive since most plant cells are turgid (turgor pressure). The contribution due to
the binding of water to colloidal particles (matric) and surfaces, termed matric
potential (Ψm), also lowers the water potential. Although it is often small enough
to be ignored, matrix potential is important when considering soil water relations.
Thus, the water potential of a plant system can be arithmetically represented by
the equation:
Ψw = Ψs + Ψp + Ψm
B. Purpose
Measurement of osmotic potential by incipisnt plasmolysis
CHAPTER IIBASIC THEORY
Now, if we were to take two containers of water, and separate them by a
semi-permeable membrane (one that allows water to go through its pores, but not
solutes like salt or sugar), and add sugar to one side, this would result in a
lowering of the kinetic energy of the water-sugar solution. Thus, from a statistical-
probability point of visw, we would expect the molecules of pure water to
encounter the membrane more often than the lower energy water molecules on the
solution side, and thus, over time, water will move from the pure water to the
solution. Of course some water molecules do go the other way, but the net
exchange favors movement into the solution. This is known as osmosis. It is a
special case of diffusion (Anonymous, 2013).
If a cell is placed in a solution which has a Ψ that is higher than that of the
cell, there will be a net movement of water into the cell. However, if the
surrounding solution has a lower Ψ than in the cell, there will be a net movement
of water out of the cell. If this latter situation continues, the plasma membrane and
cytoplasm will pull away from the cell wall, a condition known as 3 plasmolysis.
By trial and error, a concentration of bathing solution can be found that just
produces plasmolysis, and this is known as “incipisnt plasmolysis”. Thus,
incipisnt plasmolysis is defined as when @50% of the cells are plasmolyzed. At
incipisnt plasmolysis, there is no longer a pressure potential exerted by the wall
(i.e., Ψρ = 0), and therefore, under that condition, Ψ = Ψп. It should also be noted
that for solutions, Ψ = Ψп. A solution which just causes incipisnt plasmolysis thus
has a water potential (and osmotic potential) of the cell cytoplasm. Finally, since
the cell we use are highly vacuolated, it can also be assumed that the osmotic
potential of the cell is basically the vacuolar osmotic potential (Ismail, dkk. 2013).
Thus, the solution will increase in volume, and become more diluted. Over
time, this will slow the flux of water into the solution, but not stop it entirely.
However, eventually, the weight of the water will exert a backpressure on the
solution, which, if given enough time (and large enough container) will increase
the pressure on the membrane and force water molecules to go back into the pure
water. If the pressure is great enough, it can totally balance the number coming in,
and the net flux of water will cease. The amount of pressure needed to totally
balance the flows of water is known as the osmotic pressure and symbolized
aswith units of pressure (e.g., pounds per square inch, atmospheres, bars,
Megapascals) (Anonymous, 2013).
A slightly more complex theory that is often found in general biology
books (including your text, p. 117) is the “bound water” explanation. This says
that any hydrophilic solute (like sucrose or NaCl) will bind up hydrating water
and prevent it from moving freely. Therefore, the side of a semipermeable
membrane with pure water has a higher “free” water concentration than the side
with the solute molecules. According to this explanation, “free” water moves into
hypertonic solutions simply because it is diffusing down its concentration
gradisnt. Although it is popular in introductory texts, this theory is not even
mentioned in several revisws (Baumgarten and Feher, 1998; Weiss, 1996, pp.
216-222).
If the bound water explanation were true, we would expect that a greater
mass of hydrophilic solute would bind more water. Whether a certain mass of
solute is present in a few large molecules or in many small ones shouldn’t matter.
Also, when predicting osmosis, we would have to carefully consider how
hydrophilic the solute is (that is, how many water molecules it binds per
molecule). In fact, the number of molecules present does affect osmosis, and we
can predict osmosis without considering how hydrophilic the solute molecules are
(Anonymous, 2013).
Water is a simple molecule, consisting of one atom of oxygen (0) and two
hydrogen atoms (H), so that the molecular weight of only 18 g / mol. In spite of
the simplicity of the composition of the constituent atoms and small molecular
size, the water molecule has several unique characteristics. These characteristics
caused by a seriss of two H atoms on atom 0 (in center) do not form a straight
line. This circuit makes an angle of 1050. The magnitude of this angle is always
the same if the water is in solid form (ice), but rather variss if water is in liquid
form, although the average angle remains 1050. Water can dissolve more types of
chemicals compared to other liquids (Lakitan, Benjamin. 2011).
If plant cell are placed in pure water, water will initially move into the cell.
After are period of time the cell will become turgid. Turgor pressure is the
pressure exerted against the cell wall by contents of the cell. At first most water
movement is into the cell. As the turgor pressure increases water will begin to
diffuse out of the cell at a greater rate, eventually equilibrium will be reached and
water will enter and leave the cell at the same rate. This stage is used to find the
water potential of a particular cel (Anonymous, 2013).
Intake or water net expenditure by a cell occurs by osmosis, is passive
transport of water through a membrane. The combined effect of these two factors
solute concentration and pressure are called water potential. In the water potential
is important to understand is the water will move through the membrane from a
solution with high water potential to a solution with a lower potential IAR.
Components potential in water potential refers to the potential energy, which is
the capacity to perform work when water moves from areas with higher to areas
with lower (Campbell, 2000).
Potato cell contain polysaccharides starch and glycogen they are good for
storage. The potato cell is surrounded by plasma membrane it is a fluid mosaic
model, which is mosaic of phospholipids and proteins moving around they are not
solid. This is why plant cell can become turgid and flaccid because their walls
(plasma membrane) can stretch. The plasma membrane is a selectively permeabel
barrisr between the cell and the extra cellular environment. Water enters in the
cell through phospholipids (Anonymous, 2013).
Like molecular diffusion and pressure –deriven bulk flow, osmosis occurs
spontaneously in response to a driving force. In simple, diffusion, substances
move down a concentration gradisnt; in pressure-driven bulk flow, substances
move down a pressure gradisnt; in osmosis, both types of gradisnts influence
transport, he is say the direction and rate of water flow across a membrane are
determined not solely by the concentration gradisnt of water or by pressure
gradisnt, but by the sum of these two driving (Finkelstein, 1987).
CHAPTER IIIPRACTICUM METHOD
A. Place and Date
Day / date : Wednesday, March 21st 2013
Time : 10.50 Wita – 12.30 Wita
Place : Biology Laboratory third floor at west FMIPA UNM
B. Tools and Materials
1. Tools
a. Microscope
b. Cutter
c. Object and deck glass
d. Petri dish
e. Tweezers
2. Material
a. Solution of sucrose
b. Leaf of Rhoeo discolor
C. Work Procedure
1. Prepare 6 petri dish and label each petri dish by concentration sucrose
solution to be used.
2. fill each petri dish with a solution sucrose 0.1, 0:15, 0.20, 0:25, 0:30, 0:40
m.
3. Taking epidermis Rhoe discolor, then slashing or slicing the epidermal
layer purple with a knife or razor blade and slashed seek only the cell
layer.
4. Submerge the epidermis slashes on a petri dish that already contains a
certain concentration of sucrose solution with the same number of
incisions for 15 minutes.
5. After 15 minutes, take the cuts that have been soaked in a petri dish and
examined under a microscope.
6. Counting the total number of cells in one area of the fisld of vision, the
amount of cell is happened plasmolisis and the percentage of cells that
happened plasmolisis the total number of cells.
CHAPTER IVRESULT
A. Result of Practicum
Table
Effect of sucrose concentration on epidermal cells Rhoe discolor
Concentration PlasmolisisHappen %
Not Happen Plasmoliss %
PicturesCaption
0,10 60 % 50 % osmotic potential (Ψπ) for 0.1M in 27°C :-Ψπ = miRT-Ψπ = (0.1)(1)(0.082)(273+27)-Ψπ = -2.46Ψπ = 2.46
0,15 20 % 80 % osmotic potential (Ψπ) for 0.15 M in 27°C :-Ψπ = miRT-Ψπ = (0.15)(1)(0.082)(273+27)-Ψπ = -3.69Ψπ = 3.69
0,20 40 % 60 % osmotic potential (Ψπ) for 0.20M in 27°C :-Ψπ = miRT-Ψπ = (0.20)(1)(0.082)(273+27)-Ψπ = -4.96Ψπ = 4.96
0,25 70 % 30 % osmotic potential (Ψπ) for 0.25M in 27°C :-Ψπ = miRT-Ψπ = (0.25)(1)(0.082)(273+27)-Ψπ = -6.15Ψπ = 6.15
0,30 80 % 20 % osmotic potential (Ψπ) for 0.30M in 27°C :-Ψπ = miRT-Ψπ = (0.30)(1)(0.082)(273+27)-Ψπ = -7.38Ψπ = 7.38
0,40 80 % 20 % osmotic potential (Ψπ) for 0.40M in 27°C :-Ψπ = miRT-Ψπ = (0.40)(1)(0.082)(273+27)-Ψπ = -9.84Ψπ = 9.84
B. Data AnalysisBased on the data that have been obtained can be analyzed as follows:
1. At a concentration of 0.10 m sucrose solution. Epidermal cells Rhoe discolor
experisnced plasmolisis with the percentage of cells is happened plasmolisis
by 60% and 50% were not plasmolisis.
2. At a concentration of 0.15 m sucrose solution. Epidermal cells Rhoe discolor
experisnced plasmolisis with the percentage of cells is happened plasmolisis
by 20% and 80% were not plasmolisis.
3. At a concentration of 0.20 m sucrose solution. Epidermal cells Rhoe discolor
experisnced plasmolisis with the percentage of cells is happened plasmolisis
by 40% and 60% were not plasmolisis.
4. At a concentration of 0.25 m sucrose solution. Epidermal cells Rhoe discolor
experisnced plasmolisis with the percentage of cells is happened plasmolisis
by 70% and 30% were not plasmolisis.
5. At a concentration of 0.30 m sucrose solution. Epidermal cells Rhoe discolor
experisnced plasmolisis with the percentage of cells is happened plasmolisis
by 80% and 20% were not plasmolisis.
6. At a concentration of 0.40 m sucrose solution. Epidermal cells Rhoe discolor
experisnced plasmolisis with the percentage of cells is happened plasmolisis
by 80% and 20% were not plasmolisis.
C. Discussed
When Rhoeo discolor under normal circumstances, visible cell parts hexagon-
shaped cavity with cytoplasm of the cell wall purple meet. Water dripped form an
isotonic environment both inside and outside the cell, so that the normal cell
shape.
At the time of incision Rhoeo discolor leaves, soaked in a solution of sucrose
0:10, 0:15, 0:20, 0:25, 0:30, 0:40 m. So the solution is more concentrated outside
the cell than inside the cell. In accordance with the principle of osmosis, the
movement of water or solvent from a more dilute solution to a more concentrated
solutions. water will flow out of the cell vacuoles heading out because of the
pressure of osmosis.
Consequently Rhoeo discolor leaf cells lose water so purple cytoplasm away
from the cell walls shrink and as if out and rupture of the cell. Gradually the
cytoplasm fade into purple blotches. This happens because the solution sucrosa
acts as a hypertonic solution, the solution whose concentration is lower than the
fluid inside the cell.
From the analysis above, it can be derived that the dense concentration of
sucrose solution is used to soak the incision epidermis Rhoe discolor the more the
epidermal cells that undergo plasmolisis. This can be the result of differences in
water potential inside and outside the cell. Potential water in the cell is greater
than the existing water potential outside the cell. Therefore, the water potential is
proportional to the osmotic potential, the osmotic potential in the cell is greater
than the osmotic potential that exists outside the cell. This has led to the migration
of water molecules in the cell to outside the cell in the lab this time the water
molecules move from epidermal cells Rhoe discolor leading to the solution of
sucrose, resulting protoplasts epidermal cells lose water, shrink volume (cells
become wrinkled) and finally detached from the cell wall, the events that occur in
epidermal cells Rhoe discolor is commonly called the Plasmolisis.
CHAPTER VCONCLUSION AND SUGGESTION
A. Conclusion
Plasmolisis event is the release of the cell membrane in plant cells due to the
cell is in an environment that is hypertonic. Conditions hipotonis cells resulting
environmental occurrence osmosis from the cells into the environment. As a
result, water levels dropped dramatically in the cell and the cell membrane
detached from the cell wall.
A cell will undergo plasmolisis if the water potential in the cell greater than
the existing water potential outside the cell. It also means that the osmotic
potential that is inside the cell is greater than outside the cell.
B. Suggestion
1. Laboratory should provide tools that fit the needs of that practice can be
implemented with a conducive and comfortable.
2. Assistant should accompany each group to support the implementation of
practical activitiss in accordance with the desired.
3. My frisnds should understand the working procedures before entering the lab
room
BIBLIOGRAPHY
Anonymous, 2013. http://courseworkbank.info/journal. Accesed 26th march 2013
Anonymous, 2013. Lecture Water. http://employees.csbsju.edu. Accesed 26th
march 2013
Anonymous, 2013. http://biology.clemson.edu. Accesed 26th march 2013
Anonymous, 2013. http://appstate.edu. Accesed 26th march 2013.
Campbell. 2000. Biologi Campbel edisi 3. Jakarta: Erlangga.
Lakitan, Benyamin. 2011. Dasar-dasar Fisiologi Tumbuhan. Jakarta: Rajawali Pers
Finkelestein, A. (1987) Water Movement through Lipid Bilayer, Pores, and Plasma Membranes: Theory and Reality. Wiley, New York.
Taiz, Zeiger. 2002. Plant Physiology edtion 3. Sinauer Associates: England
Questions:
1. What concentration of surcose resulted in incipisnt plasmolysis, and how
did you know when it occurred?
2. Based on the above, what was the osmotic potential of the cells? Show
your calculation.
3. What were possible sources of error in this experiment?
Answer
1. In our observation, of all the sucrose concentration given all the impact
plasmolisis. But the presentation of the different plasmolisis. Experisncing
the highest plasmolisis is sucrosa solution 0:30 and 0:40 then sequentially
is 0:25, 0:10, 0:20 and presentations that have the lowest plasmolisis is
0.15 m sucrose solution.We known plasmolisis happen becouse the water
molecules move from epidermal cells Rhoe discolor leading to the solution
of sucrose, resulting protoplasts epidermal cells lose water, shrink volume
(cells become wrinkled) and finally detached from the cell wall, the events
that occur in epidermal cells Rhoe discolor is commonly called the
Plasmolisis.
2. Observation result of with use abbreviation:
osmotic potential (Ψπ) for 0.15 M in 27°C :-Ψπ = miRT-Ψπ = (0.15)(1)(0.082)(273+27)-Ψπ = -3.69Ψπ = 3.69
3. Errors that may occur in this lab are:
a. Aprentice inaccuracy when determining or calculating the number of
cells undergoing plasmolisis and the number of cells that do not
undergo plasmolisis.
b. Errors in taking the epidermis rhoe discolor, possible incision
epidermis has taken bold measures to normal size in the experiment to
be performed.
c. Sucrose solution used was not valid due to the mixture of sucrose
solution with each other this is caused by the use of a Pasteur pipette
solution simultaneously for all becouse Pasteur pipette is used only
one solution for all.
osmotic potential (Ψπ) for 0.1M in 27°C :-Ψπ = miRT-Ψπ = (0.1)(1)(0.082)(273+27)-Ψπ = -2.46Ψπ = 2.46
osmotic potential (Ψπ) for 0.20M in 27°C :-Ψπ = miRT-Ψπ = (0.20)(1)(0.082)(273+27)-Ψπ = -4.96Ψπ = 4.96
osmotic potential (Ψπ) for 0.25M in 27°C :-Ψπ = miRT-Ψπ = (0.25)(1)(0.082)(273+27)-Ψπ = -6.15Ψπ = 6.15
osmotic potential (Ψπ) for 0.30M in 27°C :-Ψπ = miRT-Ψπ = (0.30)(1)(0.082)(273+27)-Ψπ = -7.38Ψπ = 7.38
osmotic potential (Ψπ) for 0.40M in 27°C :-Ψπ = miRT-Ψπ = (0.40)(1)(0.082)(273+27)-Ψπ = -9.84Ψπ = 9.84
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