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

22 1 Chemistry and Structure of Cuticles as Related to Water and Solute Permeability
Area of epidermal cells (µm 2 )
8000
7000
6000
5000
4000
3000
2000
1000
Thickness (µm)
12
10
8
6
4
cell wall
cuticular layer
2
0
cuticle proper
0 5 10 15 20
Distance from leaf base (cm)
0
0 5 10 15 20
Distance from leaf base (cm)
Fig. 1.7 Development of epidermal cells and adaxial epidermis of Clivia miniata leaves. (Redrawn
from Riederer and Schönherr 1988)
The adaxial cuticle of Clivia miniata leaves has a laminated CP, and is ideally
suited to study cuticle development. Clivia is a monocot, and leaves grow at their
base such that cuticle age increases in direction to the leaf tip. Size of epidermal
cells, thickness of cuticles and cell wall, cutin composition, cutin biosynthesis and
fine structure have been investigated as a function of position, that is of age (Mérida
et al. 1981; Schmidt and Schönherr 1982; Lendzian and Schönherr 1983; Riederer
and Schönherr 1988).
Between position 1 cm and 5 cm, the projected area of epidermal cells increased
about ninefold from 800µm 2 to 7,000µm 2 . Afterwards, cell area no longer changed.
At the same positions, cell length increased from 50 to 250µm (Riederer and Schönherr
1988); that is, epidermis cells increased both in length and width up to position
5 cm (Fig. 1.7).
The CP was synthesised first and its thickness increased up to 3 cm from leaf
base. Fine structure also changed. Maximum thickness of CP was about 200–
250 nm, and it increased no further between 3 and 20 cm (Figs. 1.7 and 1.8 inset).
Starting at position 3 cm the cuticular layer developed, and it increased in thickness
up to position 20 cm from leaf base. Fine structure of the CL (Fig. 1.8) and
chemistry (Riederer and Schönherr 1988) changed significantly.
Lamellation of the CP is best seen at 3 cm from base. At higher positions (>4cm)
the central part of the CM has little contrast, probably because OsO4 does not penetrate
because the CP is incrusted with waxes. The cuticular layer starts to develop at
position 3 cm and increases in thickness at higher (older) positions. The CL is initially
reticulate, but in old and mature positions fine structure has disappeared. It is
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