Some investigations of ion bombardment effects on plant cell wall surfaces

Recent developments in the field of ion beam bioengineering, for example our own work demonstrating ion beam-induced transfer of exogenous macromolecules into the interior cell region, have underscored the need for a better understanding of the effects of ion bombardment on the cell wall material. We describe here, our investigations of ion beam sputtering of plant cell wall material and ion beam-induced damage to the cell wall. The presently available ion implantation simulation programs are not adequate, and experimental results are not available, either. We have indirectly estimated the surface sputtering yield of plant cell wall composed of C6H12O6-compound by remodeling the cell wall material so as to use partial mass densities and surface binding energies in the available ion implantation programs. For bombardment with a 30-keV Ar-ion beam, the sputtering yield from the cell wall is estimated to be approximately 10 atoms/ion, which is somewhat greater than the value predicted by direct program simulation, but in good agreement with experimental results. We have also performed electron microscopy on the ion-bombarded cell walls. The micrographs show novel microcrater-like structures on the cell wall subsequent to ion bombardment, which could be the ion beam-generated pathways for exogenous macromolecule transfer.