Fig. 1. Effects of bulk solution pH and Ca concentrations on roothair length. Roothairs were measured for seedlings incubated at 0.04 (•), 0.4 () and 4 () mM Ca at solution pH of 4.0, 4.5, 5, and 6. Standard errors for comparing different Ca by pH interaction means were 3.1 µm, a value smaller than the data symbols.