Investigating the effect of time on the plasmolysis of potatoes

What causes potatoes to go soft after being stored for a long time?

The purpose of this experiment is to determine how much water a potato cylinder (4 cm in length) can hold after being exposed to different amounts of time, measured in weeks, in order to better understand how time influences the quantity of water that potatoes lose. Since I believe the amount of water the potato cylinder will absorb by osmosis will be equal to the amount of water lost over time, I will determine this by measuring the change in mass of the cylinder after it has been submerged in water for 1.5 hours.

Osmosis is the passive movement of water across a cell's membrane that is only partially permeable. Since this transport is passive and not active, no ATP is required for the water to travel through the partially permeable membrane along the concentration gradient. The cytoplasm and plasma membrane are drawn away from the cell wall in plant cells, such as those found in potatoes, as water escapes the tissue of the cell by osmosis. The cell wall, on the other hand, keeps its shape because it is a semi-rigid structure made primarily of cellulose. Plasmolysis is the scientific name for this process of water loss and plasma membrane gathering. Plant cells rely on turgor pressure, which is created when water fills the cytoplasm, for support, as is visible in flowers when they wilt from a lack of water. Additionally, this explains why potatoes soften over time. Water will eventually osmotically exit cells when they are exposed to a hypertonic environment, which means that the cells already contain more water than is present outside. Because of this, potatoes that are left out for a longer period of time will eventually grow turgid because the water will be sucked out of the cells through the partially permeable membrane. The change in mass of the potatoes over time can be used to calculate how much water is lost by the cells through osmosis.

Water will migrate up the concentration gradient and into the cell cytoplasm when flaccid or plasmolyzed cells are placed in a hypotonic solution with reduced osmotic pressure. The cell cytoplasm will progressively become turgid again after this movement until an equilibrium point is reached. Because of this, the ability of the potato cells to absorb water when placed in a beaker of water increases as more water is lost from the cells through osmosis. As a result, it is possible to forecast that over time, potatoes will lose bulk as a result of water evaporation through osmosis. However, this water can be reabsorbed when placed in a hypotonic solution.

My hypothesis is that plasmolysis happens as potatoes age and hence more water is lost from them as they become softer over time. The plasmolyzed potato cells can reabsorb the water that was lost over time and become turgid once more when they are submerged in water by osmosis. As a result of the potato's increased capacity to absorb water, I predict that as the potato ages, its mass will increase. For this reason, I anticipate that the mass of the entire potato will progressively decrease over time while the mass of the potato cylinders will alter when they are submerged in water.

• Potatoes: twenty-five potatoes from the same type and batch, with about the same size and weight.
• Ruler (mm)
• Measuring cylinder (20ml)
• 5 Beakers (500ml)
• Distilled water
• Two tiles for cutting
• Cork borer for cutting potato cylinders
• Balance (g)
• Incubator set to 20°C
• Marker pen
• Stop-watch (s)

• Select twenty-five potatoes, with approximately the same size and mass, from the same batch and divide them into five groups. Label them accordingly: potatoesin group 1 with the labels 1a, 1b, 1c, 1d, 1e, potatoes in group 2 with the labels 2a, 2b etc.
• Weigh each potato and record the mass.
• Place potatoes in groups 2 to 5 into an incubator and turn the temperature to 25°C.
• Take the 5 potatoes of group 1 and using a cork borer, cut a cylinder out of the centre of each potato.
• Place each cylinder onto a tile and label these tiles according to the potato from which the cylinder was cut from. Carefully, using a millimetre ruler to cut each cylinder to a length of 4cm.
•  Take five 500ml beakers and label them a to e.
• Fill the beakers with 500ml of distilled water each.
• Using an mg balance, weigh each cylinder and record the mass in a table.
• Place each cylinder into one of the prescribed beakers and be careful to start the stopwatch at the same time. 9) After 1.5 hours, take each cylinder out of the beaker and place it on a separate tile, with the prescribed labels a to e.
• Using a mg scale, weigh the mass again.
• Record the new results in the table.
• In intervals of one week, repeat the steps 3 to 10 for the potatoes in each group, so that group two is investigated in week two, group three in week three etc.
• Make sure to record the mass of the whole potato before cutting the cylinder.

Since the scale was accurate to the nearest 0.01g, an uncertainty error of ±0.05g must be taken into account when determining the mass of each whole potato.

Since the same scale was used and was precise to the nearest 0.01g, an uncertainty error of 0.05g must be taken into account for the measurements of the entire potatoes.

By summing the measurements for each potato or cylinder and dividing the total by the number of measurements taken for each sample, in this case five, the mean average in Figure 1 and 2 was determined.

Mean Average \(\frac{al+a2+a3+a4+a5}{5}\)

Calculation of Standard Deviation and Relative Percentage Value

Excel was used to determine the Standard Deviation, which is listed in Figure 4 and 5. It displays how widely results vary from the mean on average. The relationship between the standard deviation and the mean average is depicted by the relative Percentage value. This percentage is calculated by dividing the standard deviation by the mean average and multiplying the result by 100.

Calculation of the Percentage Value for the change of mass.

The average mass loss is divided by the average beginning mass measured each week to get the percentage number. It is impossible to compare the increases in mass proportionally since biological factors affect the initial masses of both the whole potatoes and the potato cylinders. However, because the percentage value takes into account the connection between the original mass and the change in mass, it can be seen as a more accurate method of assessment.

The data point for the percentage value estimated of both whole potatoes and potato cylinders in the first week does not fit to the general trend and consequently is off the expected line of the graph, as can be seen in figures 8 and 9. Looking back at the initial data gathered for the overall change in mass It is evident that the findings from Potato D in Week 1 do not fit into the typical pattern of results since they are greater. This is true for both potatoes and the cylinders. Tables 4 and 5's standard deviation and relative percentage value amply demonstrate this point.

The relative percentage number, which depicts the correlation between the standard deviation and the mean average, allows one to compare the dispersion of the data.Small standard deviations indicate that the values are close together when they are less than 33% of the mean.The relative percentage value for all measurements is lower than 33%, as shown in tables 4 and 5. However, it is apparent that Week 1 calculations yield a higher relative percentage value than estimates for any other week. The data is quite dispersed, as shown in table 4 where a value of 31.01% is just under 33%. The results for the potato cylinders in Week 1 with a percentage value of 23.44% can be stated to be similar.

This prompted me to review the initial raw data I had gathered in Week 1 and to take the measurements from Potato D out of the equation. The unusual nature of these data, which should not be taken into account in the calculations, is indicated by the asterisk (*) next to them. The anomalous data from Potato D in week 1 had been omitted in the calculations for the percentage value for the change in mass of the whole potatoes and potato cylinders shown in Tables 10 and 11.

It is confirmed that Potato D was an unexpected result by the relative percentage values falling from 31.01 to 14.91 for whole potatoes in Week 1 and from 23.44% to 7.89% for cylinders. The newly processed data for Week 1 is much more dependable because it is much closer to the mean.