EVALUATION OF 2 APPROACHES TO THE QUANTITATIVE HISTOCHEMICAL-LOCALIZATION OF SUCROSE-P SYNTHASE IN LEAVES

Two methods for determining the quantitative localization of sucrose-P synthase in plant tissues were evaluated. The single-cell method (rap id freezing, freeze-drying, microdissection, micro-analysis) was valid ated in several ways, including comparative biochemistry, comparative histochemistry, and kinetics. In contrast, bulk isolation of cells by protoplast-forming methods resulted in loss of sucrose-P synthase acti vity. This latter approach is widely used and, as far as we are aware, can be successfully used for measurement of other enzymes. Thus, our observations form the basis for a specific caution against the use of protoplast-forming methods in an assay protocol for sucrose-P synthase .