IMPROVING CALCIUM PENETRATION: MEASUREMENT AND FACTORS AFFECTING CUTICULAR PENETRATION
We developed a finite-dose diffusion system using a Ca2+ ion-selective electrode for evaluating factors affecting cuticular penetration. Ca2+ penetration was followed using cuticular membranes (CM), enzymatically isolated from mature tomato fruit, with a finite-dose diffusion half-cell as a model system. A Ca2+ ion-selective electrode was used for the determination of Ca2+ concentration in the receiving solution (20 mM KCl). Single droplets (1μl) of CaCl2 solution were applied on the cuticular surface as a source of Ca2+. The response of the Ca2+ ion-selective electrode was rapid, and the response time to reach a constant value was usually 2–5 minutes. The electrode gave a Nernstian (linear) response for calibration solutions in the range of 10-2 to 10-4 M Ca2+. Sensitivity for Ca2+ was in the range of 1 to 5 x 10-6 M Ca2+. The electrode was fully functional for at least 3 weeks. Transcuticular penetration of Ca2+ following application of 2 to 6 μl droplets of CaCl2 at 0.05–1.0 M was readily detectable. Steady-state flow was observed for at least 60 h. About 0.80±0.65 % (n=13) of the applied Ca2+ penetrated within 19 h.
Ohkouchi, T., Bukovac, Martin J. and Noga, G. (1998). IMPROVING CALCIUM PENETRATION: MEASUREMENT AND FACTORS AFFECTING CUTICULAR PENETRATION. Acta Hortic. 466, 115-118
tomato fruit cuticles, Ca2+ ion-selective electrode