Hydrogen peroxide and lignification

The production of hydrogen peroxide in plant tissue is demonstrated quickly with a simple histochemical test. The test solution, 50 mM potassium iodide in a 4% (w/v) potato starch suspension, is applied to the cut surface of the tissue to be tested. Hydrogen peroxide oxidizes iodide ions to iodine; the iodine is complexed by the starch to form a blue-purple color. This test detects hydrogen peroxide production in cells undergoing lignification, i.e. tracheary elements and phloem fibers, and in some epidermal cells. In addition there is a rapid production of hydrogen peroxide in crushed cells. The test is negative under (i) anaerobic conditions and (ii) in the presence of catalase.