For a negative control, carborundum was applied on the surface of the leaves, then they were rubbed with a sterile cotton swab dipped into a pH 7.4 phosphate + diethyldithiocarbamate acid DIECA buffer.
Como control negativo se aplicó carborundum en la superficie de las hojas y se frotaron con un hisopo estéril humedecido con amortiguador de fosfatos + ácido dietilditiocarbámico DIECA pH.