Figure 2.

The cuticle is the first and main barrier to foliar herbicides. The cuticle proper is the real transport barrier. It is unrelated to surface wax (rods above cuticle proper) and not easily accessible by agrochemicals (white particles) and adjuvants (film above cuticle proper) or water respectively. White circles with a hyphen below indicate negative charges from carboxy groups which are particularly dense in the pectin layer (white dotted line) and limit transport of the ionized fraction of weak organic acid herbicides (modified from Aponte and Baur ³² ).