EVIDENCE OF HELICAL THYLAKOID ARRANGEMENT BY SCANNING ELECTRON-MICROSCOPY

Indirect evidence has been gained recently of the helical arrangement of single thylakoids around grana by serial transmission electron microscopic sections. However, attempts to visualise the three-dimensional structure directly remained unsuccessful, because structural details could not be resolved by scanning electron microscopy on conventionally-prepared samples. By application of the modified thiocarbohydrazide method for isolated grana samples we were able to improve the resolution on such samples below 100 Å and produce thus the first direct evidence for multiple tilted planes in a helically arranged fretwork around the surface of cylindrical grana. This structure leads towards a better understanding of the functional role of grana in photosynthetic processes. © 1979.