|MadSci Network: Botany|
Electrical conductivity (EC) depends on ions (charged atoms or molecules) in solution. Ions found in plant tissue include potassium (K+), proteins and organic acids, such as ascorbic acid and citric acid. Sugars and starch are uncharged molecules so do not conduct electricity. Therefore, the difference might be that potatoes have a higher concentration of ions in solution than lemons. Another possibility if you are measuring the EC in the intact tissue is that the tissue structure has an effect. The juice in lemons is stored in thousands of seperate juice vesicles, which could interfere with the flow of electricity because the solution is not continuous but contained in the vesicles. Potato tissue is more uniform and has no juice vesicles. A potato is a modified stem, and a lemon is a fruit. One way to test whether structure is important is to juice the lemon and liquify the potato tissue in a blender and see which juice has the highest electrical conductivity. Try it and see for yourself. The USDA website cited first below says a raw lemon contains 145 mg of potassium, 77 mg of ascorbic acid, and 1.2 grams of protein per 100 grams. A raw potato has 407 mg of potassium, 19.7 mg ascorbic acid and 1.68 grams protein per 100 grams. Potato is 81.6% water by weight and a lemon is 87.4 % by weight. That USDA data suggest potato would have the higher electrical conductivity because of its much higher potassium content. However, the USDA site does not include citric acid content and lemons contain from about 3.7 to 8.4 grams of citric acid per 100 grams. Based on these numbers, I would guess that lemon juice would have a higher EC than potato juice. References USDA National Food Database Citric acid Lemon citric acid content Re: can I get an electrical current to flow throught an apple pear...ect
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