VISUALIZATION OF CHANNELS AND CAVITIES OF CORN AND SORGHUM STARCH GRANULES

Evidence is presented that corn (maize) and sorghum starch granules ha ve channels that connect a central cavity to the external environment. A mutant sorghum starch with numerous, large surface pores was treate d with a methanolic solution of merbromin and sectioned. Light, fluore scence, and compositional backscattering electron microscopy revealed channels connecting an internal cavity to the external surface in most granules. Cavities and channels could also be seen in whole corn and sorghum starch granules treated with merbromin in methanol and viewed by fluorescence microscopy. Treatment of sorghum starch granules with an aqueous solution of merbromin revealed that the molecule penetrated the granule matrix under even slightly swelling conditions. Light mic roscopy showed cavities in unstained, whole, dry corn and sorghum star ch granules mounted in immersion oil.