Regulation of cell division in pea root tips after wounding: A possible role for ethylene

Summary Calcofluor White ST is a fluorescent brightener that has previously been shown to alter cellulose ribbon assembly in the bacteriumAcetobacter xylinum. In this report, we demonstrate that Calcofluor also disrupts cell wall assembly in the eukaryotic algaOocystis apiculata. When observed with polarization microscopy, walls altered by Calcofluor show reduced birefringence relative to controls. Electron microscopy has shown that these altered walls contain regions which consist primarily of amorphous material and which generally lack organized microfibrils. We propose that wall alteration occurs because Calcofluor binds with the glucan chains polymerized by the cellulose synthesizing enzymes as they are produced. As a consequence, the glucan chains are prevented from co-crystallizing to form microfibrils. Synthesis of normal walls resumes when Calcofluor is removed, which is consistent with our proposal that Calcofluor acts by direct physical interaction with newly synthesized wall components.Several types of fluorescent patterns at the cell wall/plasmalemma interface have also been observed following Calcofluor treatment. Fluorescent spots, striations; helical bands, and lens-shaped thickenings have been documented. Each of these patterns may be the result of the interaction of Calcofluor with cellulose at different spatial or temporal levels or from varying concentrations of the brightener itself. Helical bands and lens-shaped thickenings also have been examined with the electron microscope. Like other regions of wall alteration, they are found to contain primarily amorphous material. Finally, we note that cells with severely disrupted walls are unable to complete their normal life cycle.