Abstract
In sugar beet plants, Beta vulgaris var. saccharifera Alef. petioles serve not only as conductive tissues but also as intermediate storage pools6, 7, 8, 11, 13). Enzymatic conversion systems of sugar should be localized within the phloem and parenchyma cells of the petiole. In the previous paper5), histochemical detection for the presence of UDPG-pyrophosphorylase in parenchyma cells was reported. The histochemical detection for thc presence of phosphoglucomutase in the petiol tissues is described here. A histochemical method described by YANO12) for detecting the enzyme in cryostat sections of rabbit liver and muscle under light microscope was employed with slight modification in the present study. The composition of substrate mixture is shown in Table 1. Based on the principle, shown in Fig. 1., the activity of phosphoglucomutase was detected as the formation for diformazan which deposited in the cells in the form of dark blue granules. Procedure: Nonfixed hand-sections obtained from the raw-petiole of sugar beet cv. HKE-20 were used. After infiltration in distilled water, the sections were incubated in the test solution covered with toluene for 3 hours at room temperature (20°C). Prior to observation with a light microscope, the sections were mounted with glycerin after washing with distilled water. Histochemical observations: Dark blue granules which indicate the site of phosphoglucomutase activity were found to appear in cells of the sections that incubated in the test solution (Figs. 2-A∼E and 4-B). They were not found in the sections incubated in the substrate free mixture (Fig. 4-A). The reaction products were intensely detected in cytoplasms of guard cells (Fig. 2-B), phloems and bundle sheaths (Figs. 2-C and D). In parenchyma cells, the reaction products were moderately detected in cytoplasms, although intense reactions were detected around the nuclei. However, nuclei themselves were always negative (Figs. 2-A and E). The inhibitory effect of bellirium ion (BeSO4·4H2O), a specific inhibitor of the enzyme, was detected only in the concentration of 2 mM in the adult petiole, although this was found in the range from 4 to 5mM in the young petiole (Fig. 3). The presence of intense reaction of phosphoglucomutase in guard cells, phloems and bundle sheaths may indicate the occurrence of an active sugar metabolism in these tissue cells. In the parenchyma cells, the presence of intense reactions of the enzyme around the nuclei may suggest the interrelationship of the sugar metabolism occurred in nuclei and in cytoplasm.
