How Does The Concentration Of Water Affect The Rate Of Potato Osmosis

The aim of this experiment was to show the water potentials of young, old and damaged potatoes and different sucrose concentrations (0.15, 0.20, 0.25, 0.30, 0.35 and 0.50). It was expected that the potatoes would lose weight as the potatoes would have lower water potential when placed in a solution , and in this can be taken from the theory of osmosis which states that “the passive diffusion of water molecules across a selectively permeable membrane down a concentration gradient” (Taylor and Bruenn, 2009), moving water from a high to a low concentration, so in this case water would move from the potato tuber to the sucrose solution reducing the weight of potatoes. Pospíšilová (1970) also states that the water absorption rate of tissue will decrease if
a sucrose solution is used instead of using pure water.
This was seen clearly with the young potato which has a clear negative correlation, as the concentration of solution increases the weight of the young potato gets more negative, which proves that the potato had a high water content when compared to the sucrose concentration around it so the water moved from the potato to the solution causing the potato to lose weight. The young potato also shows a drastic decrease in weight within the 0.25M concentration and this could be because the plant cells were still ‘turgid’ before the 0.25M concentration (Nulsen et al., 1977). When cells are turgid they become swollen, increasing the overall weight of the plant. There was an increase of weight in the damaged potato in concentration of 0.2M and this can be associated to the experiment that Kosinki (2013) did where he found that a potato gained weight at 0.2M. This is because the tissues are damaged and the way that water enters and leaves cannot be easily controlled. After the increase in mass of the damaged potato there was a constant decrease in mass which follows the young potato trend which means that there was a loss of water in the tuber causing a decrease in mass as the tissues in the potato had more water than
outside. The young potato has a low concentration of 0.23091 showing the isotonic point where there is no gain or loss water (Tiaz and Zeiger). The reason the young potato reaches its saturation point quickly is because it already has a high content of water in it as if it had (Nakamura et al., 1996). Therefore it needs a low concentration of the sucrose solution in other to reach the point where the water that’s going out in the cells equates to the water coming in (Nakamura et al., 1996). It can therefore be said that the old potato would have a high concentration value considering that it has a low water content which will decrease the rate at which its saturation point will be reached (Tiaz and Zeiger).
The limitations to this study is that the time used for the experiment was not enough to see the effects properly. It could have been that the students weren’t able to use the scales properly and got incorrect results or it could have been that the scales themselves were faulty giving off the incorrect results. The potatoes may have not been cut to proper size which will give off and incorrect weight. The mixing of the concentrations could have been incorrect, little or more than they should have been.
The overall results showed a decrease in weight in all the potatoes; young, damaged and old, regardless of the increase that happened in the potato. This occurred as they were soaked in sucrose, the greater the concentration, the more the mass of the potatoes decreased. This shows us that water potential of tissue is highly dependent on the concentration within the tissue itself and the concentration within the solution.