(B) flg22-induced ROS production in Col-0 and fer-4 mutant roots under Pi-starvation conditions. Seedlings grown in either HP or LP media were treated with 1 μM flg22, RALF23 or both flg22 and RALF23 for 15 mins. Roots were harvested and stained with H2DCFDA. One representative root was shown. (C) Average H2DCFDA signal intensity in roots shown in (B). The fluorescence intensity was quantified with ImageJ. The data shown indicate the means ± SDs (n = 30, n refers to the number of roots per group); n.s., not significant; **, p < 0.01 (Student's t test). Data information: All experiments were repeated three times with similar results.  