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

4 1 Chemistry and Structure of Cuticles as Related to Water and Solute Permeability
Table 1.1 Mass per area and composition of selected cuticular membranes (data from Riederer
and Schönherr 1984)
Species CM SCL MX CU HY
(µgcm −2 ) (% of CM) (% of CM) (% of MX) (% of MX)
Fruit CM
Capsicum 1,971 10 90 61 29
Cucumis 262 20 80 55 25
Lycopersicon 2,173 7 93 69 24
Solanum 599 8 92 62 30
Leaf CM
Citrus ab 318 5 95 73 22
Clivia ad 530 20 80 64 16
Clivia ab 466 18 82 66 16
Ficus ad 458 25 75 56 19
Ficus ab 493 37 63 52 11
Hedera ad 450 19 81 60 21
Hedera ab 430 17 83 61 22
Nerium ad 1,318 39 61 45 16
Nerium ab 1,633 37 63 46 17
Olea ad 836 29 71 50 21
Pyrus cv. Conf. ad 353 31 69 46 23
Pyrus cv. Conf. ad 324 32 68 47 21
Pyrus cv. Bartlett ad 350 38 62 43 19
Pyrus cv. Bartlett ab 421 45 55 37 18
Mean (sd) 744 (602) 24 (12) 76 (12) 55 (10) 21 (4.7)
CM, cuticular membrane; SCL, soluble cuticular lipids (waxes); CU, cutin; HY, fraction
hydrolysable with HCl (polar polymers); ab, abaxial; ad, adaxial; sd, standard deviation
MX using various chemicals (boron trifluoride/methanol, methanolic HCL, KOH),
methylated cutin monomers are obtained, which after silylation can be analysed by
gas chromatography and mass spectrometry (Walton 1990).
This analytical approach shows that the major cutin monomers are derivatives of
saturated fatty acids, predominantly in the chain length of C16 and C18, carrying
hydroxyl groups in mid-chain and end positions (Table 1.2). In addition, dicarboxylic
acids having the same chain length occur in minor amounts. In some species
(e.g., Clivia miniata, Ficus elastica and Prunus laurocerasus) C18-cutin monomers
with an epoxide group in the mid-chain position have been identified (Holloway
et al. 1981). Primary fatty acids and alcohols with chain lengths varying between
C16 and C26 are also released from the MX in minor amounts. Based on extensive
studies of cutin composition, including leaves and fruits from a large number of
plant species (Holloway 1982b), cutin was classified as C16-, C18- or a mixed-type
C16/C18-cutin according to the dominating chain length of major cutin monomers
released from the MX.
Recently, molecular biological and biochemical approaches which identify the
first genes coding for the enzymes involved in cutin biosynthesis of Arabidopsis
thaliana have been carried out successfully. In this context, cutin of Arabidopsis
thaliana was shown to be primarily composed of one- and two-fold C16 and