Increasing Sucrose Concentration Deceases Change in Mass of Potato Tuber Segments; Relative Osmotic Concentration Determined by Percent Change in Mass

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The relative osmotic concentration was determined by measuring the percent change in mass of the potato tissues. Change in mass was measured of six solutions, each containing different levels of concentration (0, 0.1, 0.2, 0.3, 0.4, and 0.5). The percent change in mass decreased as sucrose concentration increased, therefore, relative osmotic concentration also decreased as sucrose concentration increased. However, the osmotic concentration of 0.2 M sucrose solution was relatively greater than that of 0.1 M sucrose solution. In sucrose concentration 0.5 M, the osmotic concentration decreased slightly from that of 0.4, but significantly from those of all other sucrose concentrations. The osmotic concentrations were greater than zero in sucrose solutions of 0, 0.1, and 0.2 M; these cells were hypertonic, meaning the solutions had more solute. The osmotic concentrations were less than zero in sucrose solutions of 0.3, 0.4, and 0.5 M; these cells were hypotonic, meaning the solutions had less solute. Osmotic concentration decreased as sucrose concentration increased and cells became more concentrated.

Figure 1. The relative osmotic concentration of the potato tissues decreases as the sucrose concentration increases. Relative osmotic concentration was measured as the percent change in mass of sucrose concentration over one hour. Results are the sucrose concentration and percent change in mass.

Table 1. Estimating osmotic concentration of potato tuber cells by change in mass method

Sucrose Concentration (molarity)
% Change in mass187.919.4-1.7-16.3-23.7

Osmosis is the movement of water across a selectively permeable membrane from a solution that has a lower concentration to a solution that has a higher concentration. Water moves down a concentration gradient which is developed when there is a greater concentration of solutes on one side of a membrane compared with the other (Kargol, 1996)....
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