Stability of MeCKs. A, Comparison of the metabolism of CKs in planta. Two-week-old Arabidopsis wild-type seedlings were treated with 1 μm
13C-labeled iP, 1MeiP, or 2MeiP by vacuum infiltration for 1 h. The seedlings were then placed in water and harvested at the indicated times. The residual amount of supplied CKs in the seedling tissues was analyzed. Asterisks represent statistically significant differences among the various treatments (one-way ANOVA, Tukey’s honestly significant difference posthoc test, P < 0.05). Error bars represent the sd of three biological replicates. B, Reactivity of MeCKs to CKX in vitro. The indicated CK compounds (50 µm) were incubated with recombinant Arabidopsis CKX2 in the presence of 2,6-dichlorophenolindophenol. Reduction of 2,6-dichlorophenolindophenol was monitored by measuring the A600 at the indicated times.