Localization of hydrogen peroxide production in Zinnia elegans L-stems

Hydrogen peroxide is required for a variety of physiological processes asso ciated with plant cell wall biosynthesis. Several recent studies have sugge sted that starch-KI could be used as an effective histochemical stain for s tudying the spatial and temporal regulation of H2O2 production during plant development. In this study, we found that detection of H2O2 in Zinnia eleg ans stems using starch-KI staining was highly dependent upon plant age, dev elopmental status, and the manner in which the tissue was handled prior to staining. An alternative staining technique based on cerium perhydroxide de position clearly showed that most of the H2O2 detected by starch-KI resulte d from wounding at the cut surfaces of stem sections. However, with cerium staining, substantial H2O2 production was apparent well below the cut surfa ce in collenchyma cell walls where previous work had demonstrated localizat ion of peroxidase activity. Co-localization of H2O2 and peroxidase in colle nchyma tissues may suggest an involvement in crosslinking of the pectins an d hemicelluloses that predominate the walls of these cells. Cerium depositi on also suggested that H2O2 production in xylem vessel walls may lag slight ly behind secondary cell wall thickening. (C) 1999 Elsevier Science Ltd. Al l rights reserved.