In the 80's, Kuriyama and Rechnitz (1981) used yellow squash,containing glutamate decarboxylase, and a CO2 electrode to measure the concentration of glutamic acid in a sample. Since then, a wide variety of plant tissues have been used as bioreceptors in different biosensor formats. These biosensors use tissue slices as sources of the enzyme that catalyses a specific reaction. The main advantages of using plant tissues in biosensors are: