Water Permeability and Fine Structure of Cuticular Membranes Isolated Enzymatically From Leaves of Clivia miniata Reg

Abstract

Summary Water permeability and fine structure of cuticles isolated enzymatically from the upper surface of Clivia miniata leaves have been investigated. Water permeability of cuticular membranes (CM) was approx. 1 x 10 -10 m s -1 . Extraction of soluble cuticular lipids (SCL) from the CM increased permeability by a factor of 200 to 400 (MX-membranes). The effect of extraction was larger with MX-membranes from young leaves than from mature ones, indicating that cutin from young leaves is more permeable than cutin from mature ones even though the membranes have the same mass. Cutin from young leaves is more permeable, because it is more polar than cutin from old leaves. Cuticular layers of young leaves stain strongly with KMnO 4 . This affinity for KMnO 4 decreases during leaf and cutin development, when the cutin becomes less polar. It is argued that the cutin from young leaves is a linear polyester. During maturation additional covalent bonds (possibly ether and peroxide bonds) are introduced and the cutin becomes less polar. Fine structure of CM and MX-membranes isolated enzymatically was compared to non-isolated cuticles. There was no indication of any deleterious effects due to isolation. All fine structural details present in non-isolated cuticles are also present in isolated ones. In particular, a laminated cuticle proper can be demonstrated with OsO 4 . Lamellae are preserved during Soxhlet extraction of cuticles. In MX-membranes the lamellar construction of the cuticle proper can also be demonstrated using KMnO 4 . It is concluded that electron lucent lamellae do not represent layers of SCL. Instead, lamellation is attributed to layers of cutin differing in polarity.