Laporan Fistum Unit I

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. 12 reaksion tube

b. Reaksion tube rack

c. Marker pens

d. Graph paper

e. Kitchen knives

f. 10 cm3 Pipettes

g. 100 cm 3 beaker

h. Pasteur pipette

i. Petri dish

2. Material

a. 0.10 M, 0.15 M, 0.20 M, 0.25 M, 0.30 M, 0.40 M Sucrose solution

b. Methylene blue

c. Potato tissue

C. Work Procedure

Chardakov’s Method

1. Prepare 12 reaksion tube and reaksion tube rak.

2. Give the label each of reaksion tube based the contentration sucrose

solution is filled ex 2 tubes labelled 0.10 M, 2 tubes labelled 0.20 M etc....

3. Filled reaction tube with sucrose solution ex 2 tube for 0.10 M, 2 tube for

0.20 M etc...

4. Prepare the potato tissue with the larger is 0.5 CM

5. Inserted potato tissue into each of reaction tube.

6. Add 1 drop of Methylene blue solution to each tube with potato tissue in

and mix it.

7. Leave the tubes for 15 minutes.

8. Take methylene blue with a Pasteur pipette done with caution. enter

pasteur pipette containing methylene blue into a test tube containing a

solution of sucrose. Pasteur pipette try right in the middle of the reaction

tube. Methylene blue spray and observe the movement of methylene blue

in the test tube. do these activities in test tubes containing 0.10 M, 0.20 M

etc .....

9. Observe the movement of methylene blue in the test tube, whether

methylene blue floats, float or sink.

Gravimetric Technique

1. Prepare 6 petri dish.

2. Give the label each of petri dish based the contentration sucrose solution is

filled ex 1 petri dish labelled 0.10 M, 1 petri dish labelled 0.20 M etc....

3. Filled petri dish with sucrose solution ex 1 petri dish for 0.10 M, 1 petri

dish for 0.20 M etc...

4. Prepare the potato tissue with the larger is 2 CM as 6 piece.

5. Weight potato tissue.

6. Inserted potato tissue into each of petri dish.

7. Leave the petri dish for 15 minutes, swirling occasionally.

8. Weigh the potatoes after being soaked in a solution of sucrose.

9. Make a table of initial weight, final weight, and final weight/initial weight

for each concentration.

CHAPTER IVRESULT

A. Result of Practicum

Chardakov’s Methods

CONCENTRATIPON OBSERVATION

0.10 +

0.15 +

0.20 +

0.25 +

0.30 +

0.40 ++

Gravimetric Technique

Concentration

Berat Berat Akhir

Berat awalAwal Akhir

0.10 M 0.30 0.30 0.30/0.30 = 1

0.15 M 0.35 0.30 0.35/0.30 = 1.16

0.20 M 0.30 0.30 0.30/0.30 = 1

0.25 M 0.30 0.30 0.30/0.30 = 1

0.30 M 0.25 0.25 0.25/0.25 = 1

0.40 M 0.40 0.30 0.40/0.30 = 1.33

B. DiscussedChardakov’s MethodGravimetric Technique

Osmosis ialah proses pergerakan molekul pelarut (contoh:air) dari satu larutan yang cair (larutan hipotonik) ke satu larutan yang lebih pekat (larutan hipertonik) melalui membran semipermiabel. Potensial osmosis selalu bernilai negative. Karena titik nol dari potensial osmosis di ambil dari air murni yang bebas ion.

Dari hasil pengamatan yang telah dilakukan, kami mendapatkan data bahwa terjadi perubahan berat. Potongan kentang yang direndam dalam larutan 0.10 M, 0.20 M, 0.25 M, 0.30 M tidak mengalami perubahan berat. Kemungkinan hal tersebut terjadi karena terjadi peristiwa isotonis yaitu jaringan kentang yang tidak mengalami penambahan maupun pengeluaran air atau tidak ada pergerakan molekul air. Sedagkan pada potongan kentang yang direndam dilarutan 0.15 M dan 0.40 M mengalami penurunan berat setelah dilakukan perendaman. Perubahan berat yang terjadi yaitu potongan kentang yang direndam di larutan 0.15 M, berat awal : 0.35 g dan berat akhir 0.30 g sehingga terjadi penurunan berat sebanyak 0.05 g sedangkan pada potongan kentang yang direndam di larutan sukrose 0.40 M, berat awal : 0.40 g dan berat akhir 0.30 g sehingga terjadi penurunan berat sebanyak 0.10 g. Kami mengamati hal ini terjadi, karena kentang bersifat hipotonik dan gula bersifat hipertonik maka air yang berada pada kentang bergerak keluar sehingga kadar air pada kentang berkurang. Dan semakin besar zat terlarut yang diserap oleh umbi kentang, makin besar air yang keluar dari umbi kentang tersebut. Hal ini di tandai dengan semakin besar selisih berat umbi setelah di rendam dalam larutan sukrosa dan di timbang kembali.Osmosis is the movement of solvent molecules (eg, water) from a liquid solution (hypotonic solution) to a solution that is more concentrated (hypertonic solution) through the membrane semipermiabel. potential osmosisalways worth negative. Since the zero point of potential osmosis purified water is taken from the free ion.From the observations that have been made, we obtain data that weight changes. Potato pieces were soaked in a solution of 12:10 M, 12:20 M, 12:25 M, 00:30 M weight unchanged. The possibility of that happening because the event occurs isotonic the potato tissue unchangedand the expenditure of water or no movement of water molecules. While the potato pieces are soaked in a solution of 0:15 M and 0:40 M experience weight after immersion. Weight changes that occur are pieces of potato soaked in a solution of 0:15

M, initial weight: 0.35 g and 0:30 g final weight resulting in weight loss as much as 0.05 g while the potato pieces are soaked in a solution of 0:40 M sucrose, initial weight: 0.40 g and weight final 0:30 g resulting in weight loss as much as 0:10 g. We observed this to happen, because potatoes are hypotonicand sugar is hypertonic, the water that is on the potato moves out so that the water content in potatoes is reduced. And the larger the solute is absorbed by the potato tuber, the greater the water out of the potato tuber. It is on the mark with the greater difference in weight of tubers after a soak in a solution of sucrose and weigh again.

CHAPTER VCONCLUSION AND SUGGESTION

A. Conclusion

A plant if soaked in a solution, the water potential in plant cells is changed depending on

the concentration and viscosity of the solution used. If a high concentration of the

network,

the water out of the network so that the weight is reduced network, the network is

called hypertonic conditions. and vice versa (hypotonic conditions). While isotonic

solution

displacement does not occur so that the weight of the water molecules fixed.

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





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