Ion Binding by Surfaces of Isolated Cuticular Membranes

One approach to the solution of problems relating to the intake and loss of nutrients by plant foliage is to separate the leaf into its various components. Ion penetration, binding, and exchange phenomena for each can then be studied. A logical beginning is with the cuticular layer which may, with some species, be separated in relatively large segments as an intact membrane. Two such enzymically isolated membranes, the stomatous green onion leaf cuticle and the astomatous tomato fruit cuticle, have been subjected to rigorous study (10). Permeability of these cuticular membranes for both inorganic cations and anions was greater from the outer to the inner surface than from the inner to the outer surfaces. Furthermore, the rate of penetration was positively related to the extent of ion binding on the surface opposite the site of initial entry (11). The degree of ion binding on the inner and outer cuticular surfaces and its relationship to surface morphology is herein described.