Fig. 4.

Involvement of ROS in the La-mediated inhibition of PR growth. (A, B) Detection of ROS production in the roots of 5-day-old wild-type seedlings exposed to 150 μM La(NO₃)₃ for periods of up to 2 d using the ROS-specific fluorescent probe DCFH-DA (A) and quantification of the ROS fluorescence intensities (B) in roots treated as in (A). Bar, 200 μm. The fluorescence intensity of the untreated roots was set to 100. (C) Quantitative RT-PCR analysis of RBOHD and RBOHF expression in the roots of the Col-0 seedlings treated with or without 150 μM La(NO₃)₃ for 2 d. The expression levels of the indicated genes in the untreated roots were set to 1. (D, E) Primary root length of Col-0 seedlings treated with or without 150 μM La(NO₃)₃ in the presence or absence of KI (1 or 2 mM) or CAT (0.2 or 0.5 mM) for 4 d (D). The data are presented relative to the La-untreated control values obtained from Col-0 seedlings in the presence or absence of KI (1 or 2 mM) or CAT (0.2 or 0.5 mM) for 4 d (E). (F) The relative root lengths of Col-0, rbohD, and rbohF seedlings treated with 150 μM La(NO₃)₃ are presented relative to the La-untreated control values obtained from Col-0, rbohD, and rbohF seedlings for 4 d. n=60. The error bars represent the SEM. Different letters indicate significantly different values (P<0.01 by Tukey’s test). **P<0.01. (This figure is available in color at JXB online.)