Fig. 4.

Electrical potential differences (∆Ψ) across the plasma membrane under steady-state conditions (A) and in response to changes in [Na⁺]_ext (∆∆Ψ; B), in 21-day-old seedlings of IR29 and Pokkali, grown with or without Si (1.67 mM). Measurements at steady-state conditions occurred at cultivar-specific Na⁺ EC₅₀ values (35 mM and 50 mM [Na⁺]_ext for IR29 and Pokkali, respectively). Measurements of membrane potential differences in response to changing [Na⁺]_ext began at an initial [Na⁺]_ext of 5 mM, at which plants had been reared (B). Different lower case letters (a, b) indicate significant differences between conditions (A; t-test, P<0.05). Data are represented as the mean ±SEM (n=5–7). Measurements taken at 30 °C in seedlings grown under a 30/20 °C (day/night) temperature cycle.