The radiolabelling of isolated Hedera helix L. (ivy) leaf cuticles was
investigated after incorporation of [C-14]acetate in foliar discs. Cu
ticle radioactivity greatly decreased as leaf age increased. The perce
ntage of radioactivity incorporated in the upper cuticles decreased fr
om 0.5% to 0.08% of the total radioactivity of foliar discs from young
to old leaves. Cuticle radioactivity was recovered in waxes, cutin an
d polar components. It was considerably greater for waxes when express
ed in terms of cuticle mass. The methodology was validated using S-eth
yl-dipropylthiocarbamate (EPTC). The radioactivity incorporation in cu
ticles was significantly reduced when 1 mM EPTC was deposited as a 20-
mu L droplet on to foliar discs 6 h before the incorporation of radiol
abelled acetate. EPTC inhibited radiolabelling of wax and cutin fracti
ons in the upper and lower cuticles. Some acetylenic fatty acid analog
ues inactivating lauric and oleic acid omega-hydroxylases, used as aci
d and sulphonate forms in the same experimental conditions as EPTC, in
duced no reduction in cuticle radiolabelling. An inhibitory effect was
observed only for the acetylenic and the saturated C-12 fatty acid an
alogues, used as tetrabutylammonium sulphonates, when applied directly
in the liquid medium supporting foliar discs. Several assumptions are
considered to explain the results of the present investigation.