Ma. Viougeas et al., STRUCTURAL-CHANGES AND PERMEABILITY OF IVY (HEDERA-HELIX L) LEAF CUTICLES IN RELATION TO LEAF DEVELOPMENT AND AFTER SELECTIVE CHEMICAL TREATMENTS, New phytologist, 130(3), 1995, pp. 337-348
The fine structure of ivy leaf cuticles was investigated as a function
of leaf development before and after cuticle isolation as well as aft
er selective extraction of cuticle components. Cuticle mass increased
with increasing age from 234.3 to 539.1 mu g cm(-2). Waxes increased f
rom 12.3 to 18.6% of cuticle mass from young to old leaves. However, p
ercentages of cutin and non-lipid constituents did not vary significan
tly with leaf age. They represented approx. 58 and 26% of the cuticle
mass, respectively. Cuticle thickness determined from electron and lig
ht microscopy increased 12-fold during leaf growth to reach 4.25 mu m
for mature leaves. Transmission electron microscopy of transverse sect
ions of non-isolated and isolated cuticles showed an outer lamellate z
one gradually merging from an inner reticulate zone the thickness of w
hich increased with leaf growth. The lamellate zone appeared very earl
y (in vitro unexpanded leaf) and was characterized by a constant thick
ness (0.2 mu m). Cuticle lamellation seemed to disappear after extract
ion of soluble cuticular wax, which confirmed intracuticular wax local
ization in lamellae. Electron-dense fibrillae observed in the reticula
te zone disappeared after acid hydrolysis showing that they are made o
f non-lipid components. X-ray diffraction confirmed the presence of cr
ystalline structures and revealed a cuticle disorganization after wax
extraction. Permeability measurements showed an increase rather than a
decrease in glyphosate and isoproturon diffusion through cuticles wit
h increasing leaf age, suggesting that the main barrier to diffusion i
s the outer lamellate zone. A considerable increase in isoproturon pen
etration through cuticles resulted from the wax extraction, demonstrat
ing the major role of wax in the control of cuticular permeability to
this herbicide.