The leaf and fruit cuticles of selected drought tolerant plants

The surface characteristics of the leaves and fruits of five drought tolerant plants viz: olive, carob, pistachio, macadamia and jojoba have been examined using gas-liquid chromatography and scanning electron microscopy. The fruits and both surfaces (adaxial and abaxial) of the leaves were all protected by well developed cuticles which ranged from substantial (200-700 mu g/cm(2)) to exceptionally thick (1-3.8 mg/cm(2)). Wax embedded within the matrix of the cuticular membrane was markedly greater on leaves and fruits from "dry-farmed" (165-770 mu g/cm(2)) than from partially irrigated (14-185 mu g/cm(2)) plants. The membranes also carried extensive deposits (13-400 mu g/cm(2)) of epicuticular wax, which occurred mainly in the form of a thick impervious crust. Pentacyclic triterpenoids were the principal components of the epicuticular waxes of olive, carob and pistachio whereas the waxes of macadamia and jojoba consisted entirely of long chain aliphatic constituents. The adaxial surfaces of species of pistacia had very few stomates (2-10/mm(2)) whilst those of olive, carob and macadamia were astomatous. Stomatal densities on the abaxial surfaces were substantially greater from irrigated (100-600/mm(2)) than from "dry-farmed" (20-30/mm(2)) plants. Trichomes were found only on olive (peltate) and jojoba (unicellular).