Periclinal penetration of potassium permanganate into mature cuticular membranes ofAgave andClivia leaves: new implications for plant cuticle development.

Staining cuticular membranes ofAgave americana andClivia miniata en bloc with potassium permanganate results in a strong contrast in the interior cuticular layer while the exterior part remains unstained. This is not caused by a selective chemical reaction with the interior part but by the unidirectional penetration of the reagent from the interior side, the outside being protected by the cuticle proper. In transverse cryosections of the cuticular membrane, permanganate penetrates nearly as easily into the exterior cuticular layer as into the interior one giving the same contrast. However, compared with the periclinal penetration into the cuticle proper this penetration is accelerated five-to tenfold by the polysaccharide network within the cuticular layer which serves as a distribution-channel system. Periclinal penetration into the cuticle proper occurs independently in each "cutin penetration unit" included between two obvious lucent lamellae and further divided into subunits.