Figure 6.

Dependence of wall extension activity of Zea m 1d on pH, concentration, and temperature pretreatment. A, Activity as a function of pH. Zea m 1d was applied at 0.3 mg mL^-1 to heat-inactivated walls from wheat coleoptiles in 50 mm DMGA adjusted to different pH values. B, Activity as a function of Zea m 1d concentration, assayed in 50 mm sodium acetate (pH 4.5). Data represent means ± se of the induced extension rate, expressed as percentage increase in length per hour (mean of at least five replicates). C, Thermostability of Zea m 1d. Purified Zea m 1d was pre-incubated for 4 h at different temperatures and then assayed (at 0.3 mg mL^-1) for wall extension activity with heat-inactivated wheat coleoptile wall in 50 mm sodium acetate (pH 4.5), with 5 mm dithiothreitol (DTT); activity is expressed as the percentage of control which was Zea m 1d incubated for the same time at 4°C. Data reported are the averages + SE of at least four measurements.