Gram's iodine reagent must be added to the plate before examination of amylase production.
Step-by-step explanation:
The starch hydrolysis test is conducted to test the presence of the enzyme amylase in the test medium.
These are confirmatory lab tests done to detect and identify the presence of bacteria which can hydrolyze starch like amylose with the help of enzymes like amylase.
The test medium for this test is agar medium in a petri dish, where soluble starch is first added to initiate the microbial growth. Once incubation period of the microbes is over, dilute iodine solution is added to the petri dish in increased quantity. Iodine is a dye which helps to clearly identify the areas which are hydrolyzed by amylase and those which are not with the help of its color.