Urea Penetration of Isolated Tomato Fruit Cuticles

Abstract

14C-urea penetration of isolated tomato (Lycopersicon esculentum Mill. cv. `Pik Red') fruit cuticular membranes (CM) was studied as a function of concentration and temperature. There was no significant effect of cuticular wax on urea penetration at 25C, permeances for the CM being 8.4 × 10-10 and dewaxed CM (DCM) 11.1 × 10-10·m·s-1. Time lags were near zero for both CM and DCM. Steady-state diffusion analysis suggests that the relatively low cuticular permeance of urea is due to low partitioning that offsets high diffusivity. Urea flux through the CM and DCM showed ≈1.5- and 1.9-fold increases, respectively, for each 10C increase between 5 and 45C. Urea flux across CM and DCM increased linearly with concentration (10 μm to 1 m) and, thus, was a first-order process.