EFFECTS OF SUPERFICIAL WAX ON LEAF WETTABILITY

Experiments are described which provide more information on the role played by superficial waxes in the natural water‐repellency of leaf surfaces. Contact angles of water were measured on a variety of leaf surfaces, before and after removal of wax, and on smooth films of the isolated superficial waxes. The differences in wettability of leaf surfaces are not wholly accounted for by differences which occur in the chemical and hydrophobic properties of their superficial waxes. Waxes isolated from leaves exhibiting contact angles less than 90° are usually more hydrophobic than the leaf surface itself. On most leaves exhibiting angles greater than 90° wax is the dominant factor governing water‐repellency, the isolated wax normally making at least a 60 % contribution to the contact angle measured on the leaf surface. Additional factors, such as roughness, responsible for the occurrence of contact angles greater than 110° on certain leaf surfaces, reside in the wax layer. The hydrophobic properties of some leaves are unaffected by chloroform washing, revealing that superficial waxes play little part in their wettability. Copyright © 1969, Wiley Blackwell. All rights reserved