Figure 2.

Effect of K⁺ and Ca²⁺ ions on the IAA-induced growth rate of maize coleoptile segments. (A) IAA-induced growth rate (µm s⁻¹ cm⁻¹) of coleoptile segments incubated in the medium with 0.0 mM K⁺ and Ca²⁺ at 0.0, 0.1 and 1.0 mM. (B) As in A but with 1.0 mM K⁺. (C) As in A and B but with 10 mM K⁺ in the medium. The growth rate of five coleoptile segments (10 mm in length) was recorded for 10 h in an intensively aerated incubation medium (5 mL segment⁻¹) by means of an angular position transducer (TWK Electronic). Coleoptile segments were first preincubated for 2 h in a control medium, whereupon IAA was added at a final concentration of 10 µM. Inset shows total elongation growth, calculated as the sum of extensions measured in 3-min intervals for 10 h. All curves are mean values of at least eight independent measurements. Bars indicate ±SE.