Dynamism of apoplast

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The following results were obtained ;(1) Five glucanases bound to barley cell walls were identified as, [1] endo-1,3 ; 1,4-glucanase, [2] endo-1,3-glucanase-1, [3] endo-1,3-glucanase-2, [4] exoglucanase-1, and [5] exoglucanase-2. The enzymes involved in 1,3 ; 1,4-glucan degradation in the cereal plants are [1] and [4].(2) The enzymic activity that converts indoleacetaldehyde to indole-3-acetic acid was found in barley cell walls. The Km was 5muM which is lower than that for the cytoplasmic enzyme with similar activity (31muM). Apoplast of dark grown squash hypocotyls containes the concentration of indole-3-acetic acid 5 times higher than the symplast.(3) Essential element, boron, which was known to be localized at cell walls, was bound to rhamnogalacturoans by a diol-ester linkage and cross-linked two polysaccharides.(4) It was suggested that when xyloglucan was breakdown during elongation growth, xyloglucans becomes susceptible to enzyme action after cellulose molecules into which zyloglucan was inserted, was degraded by endoglucanase activity.(5) In is unlikely that plant has RGD peptide homologs similar to those found on animal cells.The technique with pH dependent fluorescence dye revealed that the phosphate lever of vacuoles were homeostatically regulted by the cooperative action of mechanism wiht which the cytoplasmic phosphate level was regulated.These results clearly demonstrate that the apoplast is the site where substances prerequisite for the plant life, such as plant hormones, polysaccharide-related enzymes, or inorganic ions, are dynamically metabolized.