Histochemical analysis of POP2 promoter activity upon NaCl treatment. Ten-day-old plantlets of homozygous transgenic plants harbouring pPOP2::GUS construct grown on agar medium were transferred for 2 days on agar medium supplemented, or not (Control), with 150 mM NaCl before GUS staining. (A) GUS staining pattern in shoots of plantlets. (B-C) GUS staining pattern in roots of plantlets shown in A. (D-E) Focus on root apices visible in B and C. (F-G) Focus on areas under white boxes visible in B and C. Arrows point to primary root.