FIGURE 5.

The effect of salt stress treatment on exogenous proline uptake and beneficial effects of increased proline uptake on salt tolerance in Arabidopsis seedlings. (A) The proline uptake of wild-type and pre1-1 12-day-old seedlings following a 10 h treatment with 0.5× MS liquid medium containing 5 mM L-proline (including 2.5 mM ¹⁵N labeled L-proline) with or without 180 mM NaCl. (B,C) The seeds of wild type (Col) and the pre1-1 mutant were germinated on 0.5× MS medium containing 180 mM NaCl with or without 0.5 mM L-proline (Pro), grown for 5 days. The survival rate (B) (the number of seedlings to compile statistics ≥ 200) of Col and pre1-1 seedlings and the phenotype (C) were measured and photographed, respectively. Col, wild-type Columbia. Experiments were repeated a minimum of three times with similar results. In (A,B), the data are means ± standard error (n = 3). Different letters above columns indicate significant difference (P < 0.05, Duncan’s multiple range test).