Laporan Fistum Unit II

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





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.
















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

http://appstate.edu/

http://biology.clemson.edu/

http://employees.csbsju.edu/

http://courseworkbank.info/journal

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





Laporan Fistum Unit II

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