Location of an Enzyme in Plant Cells and Tissues (B4-3)
The picture shows typical results of the first portion of Experiment 3. Germinating corn seeds were incubated in water (A), iodine (B), tetrazolium (C), or in a peroxidase substrate (D). Note that the triangular embryo in C exhibits a high rate of respiration, the aleurone layer in D contains peroxidase and the starchy endosperm in B is stained with iodine.
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Flowering plants are multicellular organisms and different enzymes are frequently produced in different tissues and in different cell types. This concept is illustrated in the first part of the exercise where students use an enzyme histochemical procedure to show that peroxidase is produced by cells that comprise a layer in the corn seed called the aleurone as shown in the figure below. In the second part of the exercise, a similar procedure is used by the student to show that peroxidase is found in the cell wall of onion epithelial cells.