Figure 7.

Membrane potentials and depolarizations of wheat root cortical cells in response to alkali cations for plants grown in the presence or absence of K⁺. A, Membrane potential of root cortical cells of plants grown without K⁺ when the root was externally perfused with 100 μm Tris⁺ (open bars) and 100 μm K⁺, Cs⁺, or Rb⁺ (solid bars). B, Membrane potential of root cortical cells of plants grown in 1 mm K⁺ when the root was externally perfused with 100 μm Tris⁺ (open bars) and 100 μm K⁺, Cs⁺, or Rb⁺ (solid bars). C, Membrane depolarizations induced by 100 μm K⁺, Cs⁺, or Rb⁺ in K⁺-deprived plants (striped bars) and K⁺-supplied (1 mm) plants (solid bars). In K⁺-deprived plants 100 μm K⁺, Cs⁺, and Rb⁺ depolarized the membrane by 66.4 ± 9 mV (n = 13), 32 ± 8.8 mV (n = 4), and 60.5 ± 9 mV (n = 4), respectively. Corresponding values for 1 mm K⁺-grown plants were 26.4 ± 9 mV (n = 7), 8.3 ± 1.9 mV (n = 6), and 25 ± 6.8 mV (n = 7), respectively.