Encyclopedia of Experiments: Biology
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Transcript
Digestible carbohydrates are the non-structural components of plant tissue, and they function as a reserve energy source for plant growth and metabolism.
To quantify the non-structural carbohydrates, take a measured amount of plant tissue in a tube. Add diluted sulfuric acid to the tube, and heat the sample. Upon heating, sulfuric acid hydrolyzes the polysaccharides of the digestible carbohydrates into their respective monosaccharide subunits.
Cool the sample. Centrifuge the tube to pellet the undigested plant material and obtain a supernatant containing the monosaccharides.
Aspirate the supernatant into a fresh tube, and treat the monosaccharides with phenol solution, followed by the addition of sulfuric acid. Vortex the tube to mix the content and incubate.
During incubation, sulfuric acid dehydrates the monosaccharides to produce furfural derivatives. These furfural derivatives react with the phenol to produce a yellow-gold solution.
Spectroscopically determine the absorbance of the yellow-gold solution at 490 nanometers, which corresponds to the carbohydrate content in the plant sample.
Next, take various concentrations of glucose solutions and repeat the phenol-sulfuric acid treatment to yield different color intensities, and plot a standard curve. Compare the absorbance value of the unknown carbohydrate sample with the glucose standard to obtain the content of digestible carbohydrates in the plant tissue.
