LOCALIZATION OF HYDROGEN-PEROXIDE PRODUCTION IN PISUM-SATIVUM L USINGEPI-POLARIZATION MICROSCOPY TO FOLLOW CERIUM PERHYDROXIDE DEPOSITION

Cerium is becoming an increasingly popular reagent for histochemical l ocalization of oxidases and phosphatases because it combines directly with reaction products to form fine precipitates of electron-dense mat erials that can be easily detected using transmission electron microsc opy or laser confocal scanning microscopy. We used epi-polarization mi croscopy to detect cerium perhydroxide deposits formed when H2O2 was p roduced by diamine oxidase in pea (Pisum sativum L.) epicotyls exposed to exogenous putrescine. Diamine oxidase activity was abundant in cor tical cell walls but showed little, if any, association with vascular tissues. Maps of cerium deposition generated using scanning electron m icroscopy/x-ray microanalysis verified these observations. This study demonstrates the use of epi-polarization microscopy to follow cerium d eposition, and the ready accessibility of this microscopy technique sh ould facilitate more widespread use of cerium for plant histochemistry and cytochemistry.