Oversensitivity of pop2-1 mutant to ionic stress. Four-day-old seedlings of WT and pop2-1 were transferred to agar medium supplemented with various concentrations of salts or osmoticum. After transfer, root apex was marked and primary root growth was recorded after 6 days. Primary root growth on agar medium supplemented with NaCl (A), KCl (B), Mannitol (C) and LiCl (D). Results are the mean ± S.E. of measurements made on at least 16 plants distributed over three plates.