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An Experiment to Determine the Water Potential (Ψ) of a Plant Tissue, using Discs of Beetroot

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Introduction

An Experiment to Determine the Water Potential (?) of a Plant Tissue, using Discs of Beetroot Introduction Water potential (?) is the measurement of the ability of water molecules to move within a cell. A high water potential (?) is achieved when there is a high water concentration within a cell. The water molecules create an outward force on the cell membrane and wall, which makes the pressure within the cell high. Plant cells with a high water potential (?) become turgid, because of the cell wall's ability to stretch slightly to reduce the pressure within the cell. Animal cells do not have cell walls and therefore lack in the ability to reduce this pressure. If the water potential (?) in an animal cell becomes too great, the cell membrane will break and the cell will have burst under the pressure. The concentration of water in a cell is controlled by several factors: * Solute potential (?s) - If there is a higher water concentration in the cell than there is in the surrounding solution, water molecules will move out of the cell. ...read more.

Middle

These cells will gradually become turgid and increase in mass. If the water potential is highest in the cells, the water molecules will move from the cells into the surrounding solution. The cell will decrease in mass and become flaccid. Prediction The beetroot discs will increase in mass when the sucrose solution has a higher water potential (?) than the beetroot cells., because there will be a net movement of water molecules from the high water concentration, in the solution, to a low water concentration, in the beetroot cells, by the process of Osmosis. Osmosis will occur until equilibrium between the beetroot cells and the sucrose solution is achieved. The increase in mass will indicate that the water potential of the beetroot cell is lower than that of the surrounding sucrose solution. The beetroot discs will become flaccid and decrease in mass if the water potential of the surrounding solution is lower than the water potential inside the beetroot cells. Osmosis will not occur if the water potential of the sucrose solution and the water potential of the cell's cytoplasm are equal. ...read more.

Conclusion

Six of the beetroot discs were placed in each of the six test tubes and left, with the bung on, for an hour. After an hour, the discs were removed from the solutions, blotted slightly, and weighed. The original mass and final mass for each of the six concentrations were recorded. From these values, the mass change (loss or gain) could be calculated. Results Conc. Of Sucrose Solution Starting mass (g) Final mass (g) Change in mass (g) 0.00 0.50 0.60 +0.10 0.10 0.60 0.70 +0.10 0.25 0.60 0.70 +0.10 0.50 0.70 0.75 +0.05 0.75 0.55 0.50 -0.05 1.00 0.65 0.55 -0.10 From the results table above, we can calculate the % change in mass by using the formula: % change in mass = change in mass � initial mass x 100 Conc. of solution (molarity) % Change in mass 0.00 +0.10 � 0.50 x 100 = 20.0 % 0.10 +0.10 � 0.60 x 100 = 16.7 % 0.25 +0.10 � 0.60 x 100 = 16.7 % 0.50 +0.05 � 0.70 x 100 = 7.14 % 0.75 -0.05 � 0.55 x 100 = -9.09 % 1.00 -0.10 � 0.65 x 100 = -15.3 % ...read more.

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Here's what a teacher thought of this essay

3 star(s)

This is a good draft of a practical investigation.
The language used is scientific and the results are presented well.
The introduction is strong and lays out the foundation for the investigation.
The structure of the report is also nearly correct. However, it is missing a finished conclusion and evaluation.
An improvement is also required in several areas, such as labeling of tables and referencing of sources.
*** (3 stars)

Marked by teacher Luke Smithen 01/05/2013

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