DETERMINATION OF THE DISTRIBUTION AND REACTION OF POLYSACCHARIDES IN WOOD CELL-WALLS BY THE ISOTOPE TRACER TECHNIQUE .6. SELECTIVE RADIO-LABELING OF MANNAN IN GINKGO (GINKGO-BILOBA)

D-Mannose-[2-H-3] and GDP (guanosine diphosphate)-D-mannose-[mannose-1 -H-3] were administered to the shoots of ginkgo (Ginkgo biloba L.) to label mannan selectively in the cell walls. To suppress the incorporat ion of radioactivity into the lignin and cellulose, the precursors wer e administered in the presence of the inhibitor of phenylalanine ammon ia-lyase (PAL): namely, L-alpha-aminooxy-beta-phenylpropionic acid (AO PP) and the inhibitor of glucan synthesis: namely, 2-deoxy-D-glucose ( 2-DG) and 2.6-dichlorobenzonitrile (2.6-DCB). When D-mannose-[2-H-3] w as administered in the absence of the inhibitors, great radioactivitie s were found in the mannose and glucose obtained by sulfuric acid hydr olysis of the newly-formed xylem, and also in the vanillin obtained by nitrobenzene oxidation. These results indicate that the radioactivity was incorporated not only into mannan but also into cellulose and lig nin. When D-mannose-[2-H-3] was administered in the presence of both A OPP and 2-DG, the radioactivities of vanillin and glucose were decreas ed but that of mannose was not decreased. These results indicate that the incorporations of radioactivities into lignin and cellulose were s uppressed by the inhibitors, but the incorporation into mannan was not interfered with. The treatment with 2,6-DCB lessened the incorporatio ns of radioactivity into vanillin, xylose, mannose, and glucose of the newly formed xylem considerably which indicated that 2,6-DCB disturbe d the metabolic activities of the plant fatally. Consequently, the sel ective radiolabeling of mannan in ginkgo was achieved by the administr ation of D-mannose-[2-H-3], in the presence of both AOPP and 2-DG, to a growing stem. In the case of GDP-D-mannose-[mannose-1-H-3], the radi oactivity incorporated into the newly-formed xylem was very little, an d the selectivity in labeling and the effects of the inhibitors were n ot clear.