Fig. 2.

Penetration of roots into hard media is compromised in pzo1 mutants. (A) Root length of Arabidopsis roots grown 9 d vertically at 60° to stimulate growth into the MS media. Black arrowheads indicate roots within the MS media and white arrowheads indicate root growth on the surface of MS media. (B) Root length of WT and pzo1 mutants 9 d after germination (n = 30 to 36; mean ± SD). (C) Representative plate of 18-d-old Arabidopsis seedlings challenged by root barriers. The more visible roots have not penetrated the barrier and are on the surface of the MS media. WT and mutants were grown vertically at 90° on normal MS media (0.5× MS + 8.5 g/L agar) before reaching the barrier (0.5× MS + 12 g/L agar). (D) The percentage of roots that penetrate barriers of different concentrations of agar as indicated (n = 8 to 11 plates) and each plate consists of 7 to 12 seedlings. (E) Representative plate of 2-wk-old Arabidopsis seedlings challenged by root barriers indicating the different root growth length in the denser media (imaged brightness was adjusted for clarity). White arrowheads indicate roots within the MS media and black arrowheads indicate root growth on the surface of MS media or roots that did not penetrate the barrier. (F) Root lengths of 2-wk-old seedlings that have penetrated the barriers (indicated) (n = 25 to 28, mean ± SD). The results were analyzed with two-way ANOVA and Tukey’s multiple comparison test. **P < 0.01, ***P < 0.001.