STUDIES ON PLANT CUTICLE III. THE COMPOSITION OF THE CUTICLE OF APPLE LEAVES AND FRUITS

The levels of deposition of the waxy and cutin components of the cuticles of the mature leaves and developing fruits of the Merton Worcester and Cox's Orange Pippin varieties of apple over a period of 4 months are reported. The waxy materials on the leaves remain approximately constant at 20 mu g./cm(2)., and the cutin at about 100 mu g./cm(2). of surface. The waxy and cutin deposits on the fruits increase markedly during the period of development, the wax and oil present on the surface and embedded within the cutin rising to 500 mu g./cm(2). and the cutin to a little under 1000 mu g./cm(2). of surface. Phenolic and acidic substances in the cuticles of the fruits are determined, and the possibility of their occurrence in surface deposits on the leaves is discussed. An examination is made of the effect of nutrient deficiency upon the formation of waxy and phenolic substances in the leaves. Nitrogen deficiency in Worcester Pearmain leaves leads to a reduced deposition of waxy materials, and nitrogen, phosphorus and potassium deficiency results in higher contents of phenolic compounds. The separation and nature of the waxy covering on leaves, the effect of environmental conditions on its formation, and its importance in relation to the application of crop protection chemicals are discussed.