ELECTRON-DENSE MATERIAL IN THE CELL-WALL PLASMA-MEMBRANE INTERFACE OF SPECIALIZED CORTICAL-CELLS OF PEANUT NODULES

The nitrogen-fixing peanut root nodules have 2-3 layers of specialized cortical cells surrounding the infected zone. These cells are morphologically distinct from the other cortical cells due to the presence of prominent amyloplasts, lipid bodies (oleosomes), large microbodies and localized pockets of electron-dense material at the plasma membrane-cell wall interface. The material is resistant to solubilization by hexane and chloroform. Electron density is enhanced by p-phenylenediamine staining and heavy metal ions such as iron, uranium and osmium. The silver proteinate staining method for suberin has shown positive results. Peroxidative activity can be demonstrated by diaminobenzidine reaction. The material appears to be proteinaceous, but could be complexed with suberin or phenolics. Although the exact nature of this material remains to be clarified, its unique position in the cells of specialized tissue of the cortex relates it to the regulation of bidirectional transport of gases and solutes during symbiosis in the root nodules. © 1993 Academic Press. All rights reserved.