BI 335 PRACTICAL NUMBER ONE
Introduction
Water potential within a plant cell is the force behind the movement of water molecules, determining how water moves within the plant. It is crucial for the plant to regulate its water potential to ensure proper functioning and health. This pressure prevents cells from bursting and maintains the balance of water movement, essential for processes like osmosis. Understanding water potential allows us to predict the direction of water movement through living plant tissue, crucial for maintaining equilibrium within the cell. By using the concept of water potential, we can better comprehend how water moves through plant cells and the impact it has on overall plant health and function. However, in the world of plant physiology, the potato has long been a valuable subject for scientific study. From its importance as a staple food crop to its unique characteristics as a model organism, the potato offers a wealth of information on how plants function and adapt to their environments. One key aspect of potato biology that researchers often investigate is water potential, the driving force behind water movement within plant cells. By conducting practical experiments on potato tissue, scientists can gain insights into how water potential influences processes like osmosis and ultimately affects the health and growth of plants. Through the lens of the humble potato, we can uncover the intricate mechanisms that govern water movement in plant cells and better understand how these processes shape the world of plant biology
Materials
The materials used in lab during the practical were 6x boiling tubes, fresh potato, scalpel, mass balance, sugar concentration of various solution (0.2M, 0.4M, 0.6M, 0.8M, 1.0M), distill water in a wash bottle, plastic wrap and thermometer those made available to conduct the practical.
Procedures and direction
Firstly, pour 20mls of assigned solution provided into the boiling tube. Then potato was sliced into six equal cylinder. Secondly, from the sliced potatoes were placed on the mass balance and reading were taken. Then cylinders were placed into the boiling tubes with the assigned solution and cover by left it for overnight. Next day, cylinders were removed from the boiling tubes and finally, record the final mass of six potatoes inside the each tubes and determined the temperature of the room. Then all the results were plotted on the table respectively and from initial to final reading and plotted on the graph against the results obtained.
Results
%Δ mass = (mass final – mass initial) / mass initial
Beaker containing Initial mass Final Mass Mass difference %change in mass
Distill water 1.38g 1.60g 0.22g 15.94%
0.2M 1.40g 1.40g 0g 0 %
0.4M 1.36g 1.18g -0.18g -13.24%
0.6M 1.31g 1.06g -0.25g -19.08%
0.8M 1.40g 1.14g -0.26g -18.57%
1.0M 1.29g 0.83g -0.46g -35.66%
The results were presented on a graph against the percentage change in mass against the concentration of sucrose molarity
The molar concentration of the potato cell is 0.2M
The solute potential can be find using the formula given below
Ψ = -iCRT where
i = the ionization
C = molar sucrose concentration at equilibrium
R = pressure constant (0.0831litres bar per mole
T = temperature K (273 + ℃)
Givens
i= (-1) (0.2M) (0.0831) (25℃ +273 = 298℃)
= -4.9527
Ψ = -4.94 bars
Explain how you would determine the molarity of a potato
In the given data, the molarity of the potato cell is determined to be 0.2M based on the percentage change in mass. The concentration where the percentage change in mass matches that of the potato cell is the molarity of the potato.
Complete the post lab questions
a.if all the potatoes cores allowed to dehydrated, by sitting in the open air would the water potential of the potato cell decrease or increase. Why?
If the potato cores are allowed to dehydrate by sitting in the open air, the water potential of the potato cell would decrease. This is because the water potential is a measure of the potential of water to move from one place to another, and as the potato cores lose water and dehydrate, there would be a decrease in the amount of free water molecules available in the cell. This would result in a decrease in the water potential of the potato cell.
b.If the plant cell has the lower water potential than its surrounding environment and if pressure is equal to zero, is the cell hypertonic (in terms of solute concentration) or hypotonic to its environment. Will the cell loss or gain water?
The cell would be hypertonic to its environment in terms of solute concentration. Since water moves from areas of higher water potential to lower water potential, the cell would lose water to its environment.
c.if the water potential for the sucrose solution is dialysis bag is -6.25 bars and it is immerse in the cup of sucrose solution having a water potential of -3.36 bars and if the water potential inside and outside the bag is zero, will the bag gain or lose mass. Explain your answers
The bag will lose mass. This is because water will move from the area of higher water potential (-3.36 bars) to the area of lower water potential (-6.25 bars) in an attempt to reach equilibrium. Since the water potential inside and outside the bag is zero, water will move out of the bag into the sucrose solution, causing the bag to lose mass.
Discussion
The results from the experiment show a clear trend in the percentage change in mass of potato cores as the molarity of the sucrose solution increases. As the concentration of sucrose solution increases, there is a corresponding decrease in the mass of the potato cores. This is indicative of the process of osmosis, where water moves from an area of higher water potential (inside the potato) to an area of lower water potential (the sucrose solution) through a semi-permeable membrane.
The data presented in the table and graph clearly demonstrate that the molarity of the potato cell is approximately 0.2M based on the percentage change in mass. The cell is at equilibrium when the percentage change in mass matches that of the 0.2M sucrose solution. This can be further confirmed by calculating the solute potential of the potato cell, which was determined to be -4.94 bars.
In terms of practical implications, these findings have significance in understanding the osmotic processes that occur within plant cells. The movement of water in and out of cells is crucial for maintaining cell turgidity and overall function. The experiment highlights how changes in solute concentration can impact water movement and ultimately affect the overall mass of the potato cores.
Overall, the experiment successfully demonstrates the principles of osmosis and provides valuable insights into the molarity and water potential of plant cells. Further studies can be conducted to explore the effects of different solutes on osmotic processes and cellular function. The data obtained from this experiment can serve as a basis for further research and understanding of plant physiology
Conclusion
In conclusion, the experiment on osmosis using potato cores immersed in different concentrations of sucrose solutions has provided valuable insights into the principles of water movement in plant cells. The results clearly show a direct relationship between the molarity of the sucrose solution and the percentage change in mass of the potato cores, indicating the process of osmosis in action. By determining that the molarity of the potato cell is approximately 0.2M based on the percentage change in mass, and calculating the solute potential of the potato cell to be -4.94 bars, we have gained a better understanding of the equilibrium state and water potential within the cell. These findings have practical implications in understanding the osmotic processes that are vital for maintaining cell turgidity and function in plants. For all, the experiment has successfully demonstrated how changes in solute concentration can affect water movement and ultimately impact the mass of plant cells. This study provides a foundation for further research on osmotic processes and cellular physiology. By exploring the effects of different solutes on osmosis, researchers can deepen their understanding of plant physiology and potentially discover new applications in agriculture and biotechnology. Recommendation:
Based on the results and analysis of the experiment on osmosis using potato cores, it is recommended to further explore the effects of different solutes on osmotic processes in plant cells. This could involve studying the impact of various concentrations and types of solutes on water movement and cell turgidity, as well as investigating the potential applications of these findings in agriculture and biotechnology.
To take it into the further the, one potential gap that can be explored in future research is the effect of temperature on osmotic processes in plant cells. By conducting experiments at different temperatures and analyzing the resulting changes in water movement and cell mass, researchers can gain insights into how temperature influences osmosis and the overall physiological processes of plants. This could have implications for understanding how plants adapt to environmental changes and how temperature fluctuations affect their growth and survival. Further research in this area could contribute to a deeper understanding of plant physiology and potentially lead to the development of novel strategies for crop improvement and stress tolerance in plants.
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