The xth17 mutant has altered root lengths, reduced Al sensitivity, and reduced Al accumulation. A, Schematic structure of the xth17 mutant locus carrying a T-DNA insertion in the third exon. The black and white boxes represent the coding and untranslated regions, respectively. B Semiquantitative RT-PCR study of XTH17 transcripts. C, The wild type (WT) and xth17 grown on MS plates without (–Al) or with 50 µm Al (+Al). D, Root elongation of the wild type and xth17 without (control check [CK]) or with (Al) 50 µm Al. Plants with approximately 1-cm roots were grown in agar medium containing 0 or 50 µm Al for 24 h. Root elongation was measured before and after treatment. Data are means ± sd (n = 10). The asterisk shows a significant difference at P < 0.05 by Student’s t test. E, Root Al content of the wild type and xth17. Data are means ± sd (n = 4). Columns with different letters are significantly different at P < 0.05. FW, Fresh weight.