sections of the samples were cut using a diamond knife (Diatome45, Switzerland) on a Richert Jung Ultra microtome (Austria) andmounted on the 200 mesh copper grids. Sections were stained withuranylacetate followed by lead citrate using the method of Xu et al.(2008). The samples were investigated by using transmission elec-tron microscope (TEM) (Hitachi, H-7100, Tokyo, Japan).