Figure 3.

NH₄⁺ exerts a differential effect on the transport of Rb⁺ in barley plants grown in different ionic environments. The short-term effect of 5 mm NH₄⁺, in combination with the presence or the absence of 100 μm Na⁺, on the uptake of Rb⁺ was determined at 100 μm Rb⁺ for plants previously exposed for 3 d to the absence of K⁺ in the presence of 5 mm NH₄⁺ (A), the absence of both K⁺ and NH₄⁺ (B), 100 μm K⁺ in the presence of 5 mm of NH₄⁺ (C), and 100 μm K⁺ in the absence of NH₄⁺ (D). All growth solutions contained 100 μm Na⁺. Note the use of a different scale in B. Results given are the average values of two separate experiments consisting of three and five independent replicates. For each growth condition, the presence of the same letter on two columns indicates the absence of significant differences at P = 0.05.