Temp Effects of Temperature Stress

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Effects of Temperature Stress on the Cell Membranes of the Common Beet

In this experiment, the effects of different temperatures on the integrity of cell membranes in the common beet will be assessed. It is hypothesized that both extremely high and extremely low temperatures will lead to a breakdown of the cell membranes of this plant, due to the breakdown of plant material at higher temperatures and the rupture of cells and cell membranes due to the expansion of freezing water at temperatures below the freezing point.

Cell membranes are vital to life, keeping the constituent elements of a cell contained and thus functioning in tandem with each other as they are supposed to, allowing individual cells to contribute to the overall success of a given organ and thus of an organism as a whole (Lund et al. 2000). Research has shown that temperature can have major effects on the integrity of cell membranes, both due to forces within the cell and in intracellular material, especially when exposure to sub-freezing temperatures is accompanied by exposure to external ice (Toner et al. 2009). Other types of stress can increase the deformability of cell membranes, leading to a host of potential problems in the development of a living organism and again demonstrating the supreme importance to life that something as small and as seemingly simple as a cell membrane presents (Bochu et al. 2000). The additional knowledge that this experiment will provide will assist in the understanding of how cell membranes respond to temperature stress, suggesting methods for the care of cell membranes and the prevention of cell membrane harm or destruction during exposures to extreme temperatures.

Materials and Methods

Necessary equipment for this experiment included a beaker, six identical test tubes that had been carefully cleaned and dried, and a pair of forceps. Also required were a refrigerator and a freezer, both with accurate temperature controls and internal thermometers, as well as hot and cold running water and a thermometer for the creation of water baths at varying temperatures well above the freezing point. A single large beet and a corer were also utilized for the experiment. Six identical cylinders were taken from the beet, rinsed in the beaker for a period of two minutes, and then placed individually in each of the test tubes using the forceps. Test tubes were labeled 1 through 6; tube 5 was placed in the refrigerator at a temperature of 5 degrees Celsius and tube 6 was placed in the freezer at -5 degrees Celsius. Tubes 1 through 4 were placed one at a time in water baths at varying temperatures -- 20, 45, 50, and 70 degrees Celsius. Beet samples were soaked in the water baths for a period of one minute, and were then returned to their test tubes that were then filled with 10mL of distilled water, in which they soaked for twenty minutes. All six beet samples were then examined for the depth of their color using a comparative scale. The absorbance of light of each sample after treatment was also measured and recorded.

Results

The samples that had been exposed to the highest and the lowest temperatures showed the greatest depth of color and higher rates of absorbance, suggesting that cell membranes in these samples had ruptured and released the betacyanin that gives the common beet its distinctive red shade and helped make these samples more opaque. Samples 1 and 2, which had been immersed in water baths of 70 and 55 degrees Celsius respectively, had respective color intensities of 5 and 4 and absorbance measures of .228 and .116. Sample 6, which had been exposed to below-freezing temperatures, had a color intensity of 7 and an absorbance of .472. Samples 3 and 4 had color intensities of 1 and absorbance measurements of .016 and .020, respectively, while sample 5 had a color intensity of 0 and an absorbance of .016. The differences in these samples were not seen to be especially significant, and likely would not prove to be statistically significant given repeated experimentation.