Water and Solute Permeability of Plant Cuticles: Measurement and ...

4.6 Water Permeability of Isolated Astomatous Cuticular Membranes 115
Fig. 4.22 Transport chamber used for measuring the flux of 3 H-labelled water from the donor
across stomatous cuticles into the receiver. In the receiver was a water-saturated filter paper
(depicted in dark blue) absorbing 3 H-labelled water which diffused across the CM. The revolving
rod allows sampling of the receiver without changing the atmosphere in the receiver. (Modified
from Santrucek et al. 2004)
The fact that resistance of fatty alcohols is a function of log nC could explain why
evolution selected very long chain wax monomers for building a water barrier. At
ambient temperatures these monomers are in the solid state, and very small amounts
of 1–2 µgcm −2 suffice. We are again confronted with the question why wax coverage
is much higher with most plants (Tables 1.1, 4.6, 4.7 and 4.11). Leaves can be
subjected to considerable abiotic (e.g., wind, rain, ice and storm) and biotic forces
(e.g., insects, fungi and bacteria). This should lead to a continuous disturbance of
a highly ordered wax structures on the leaf surface, and losses of wax might even
occur during the season. A fast and efficient compensation of this disturbance, keeping
the cuticular transport barrier intact, might require fairly high amounts of wax