Electron microscopic cytochemistry of cyclopropenoids in cottonseed (Gossypium hirsutum L.) tissues

An electron microscopic cytochemical procedure for locating cyclopropenoids (CYP) in oilseeds is proposed. The procedure is based on the fact that metallic silver is produced when AgNO3 reacts with CYP. Since so many other compounds react with AgNO3, we treated specimens that do and not contain CYP with AgNO3 and looked for electron-dense stains that were unique to CYP(+) seeds. Virtually everything in all seed specimens, regardless of the presence or absence of CYP, was stained. However, cottonseeds contained two additional staining constituents not found in controls: (i) certain large, intracellular droplets, and (ii) the cuticles, both occurring exclusively in the axial organs. Extraction of the speciments with ether abolished the stainability of the droplets but did not affect cuticles. Arguments for the validity of the test are presented.