Fig 1.
The effect of salinity stress on the selected accessions.
(A) Col-0 and the selected accessions seedlings exposed for 6 days to a medium containing 0 mM (uppermost panel), 150 mM (upper panel), 180 mM (middle panel) and 200 mM (lower panel) NaCl. a: Col-0; b: Mog-11; c: Looe-2; d: Wil-1; e: Bs-1; f: Nd-1; g: Sav-0; h: Got-1. Bar = 0.5 cm. (B) Elongation of the primary root of Col-0 and the selected accessions after a 9 day exposure to 0 or 150 mM NaCl. Values represent the mean percentages of root length achieved in the absence of NaCl stress. (C) Bleaching of the cotyledons of Col-0 and the selected accessions exposed for 6 days to 200 mM NaCl. (D) Chlorophyll content of Col-0 and the selected accessions exposed to 200 mM NaCl for 5 days. (E) MDA content of Col-0 and the selected accessions exposed to 0 or 200 mM NaCl for 36 h. All experiments were run in triplicate and involved at least 20 seedlings per assay. Values given as mean ± SE (n = 3). Significant differences from the performance of Col-0 accession are indicated by * or ** (P < 0.05, P < 0.01).
Fig 2.
Changes in ion contents, Na+/K+ ratio and net K+ fluxes of Col-0 and the selected accessions.
The whole plants treated with 0 or 200 mM for 12 h were collected and subjected to the determination. (A) Na+ content, (B) K+ content, (C) Na+/K+ ratio and (D) Net K+ fluxes in root tips. Different net K+ fluxes were measured respectively in mature zones of the accessions exposed to 100 mM NaCl for 0 or 3 h, Values are mean ± SE (n = 6–15 seedlings) from three independent experiments. Significant differences from the performance of Col-0 accession are indicated by * (P < 0.05).
Fig 3.
Expression analysis of genes related to K+ transport by qRT-PCR.
The transcript levels of (A) HAK5, (B) CHX17 and (C) KUP1 in Col-0 and the selected accessions exposed to 100 mM NaCl for 0, 3 and 6 h. Values given as mean ± SE (n = 3). Significant differences from Col-0 accession at the same time point are indicated by * or ** (P < 0.05, P < 0.01).
Fig 4.
Expression analysis of genes related to Na+ transport by qRT-PCR.
The transcript levels of (A) SOS1, (B) SOS2, (C) SOS3, (D) NHX1 and (E) HKT1;1 in Col-0 and the selected accessions exposed to 100 mM NaCl for 0, 3 and 6 h. Values given as mean ± SE (n = 3). Significant differences from Col-0 accession at the same time point are indicated by * (P < 0.05).
Fig 5.
The contents of compatible solutes.
(A) The content of proline in Col-0 and the selected accessions exposed to 0 or 200 mM NaCl for 36 h. (B) The contents of soluble proteins and (C) soluble sugar in Col-0 and the selected accessions exposed to 0 or 200 mM NaCl for 12 h. Values given as mean ± SE (n = 3), each replicate comprised at least 15 seedlings. Significant differences from the performance of Col-0 accession are indicated by * or ** (P < 0.05, P < 0.01).
Fig 6.
Expression analysis of genes related to proline degradation by qRT-PCR.
The transcript levels of (A) ProDH1 and (B) P5CDH in Col-0 and the selected accessions exposed to 100 mM NaCl for 0, 3 and 6 h. Values given as mean ± SE (n = 3). Significant differences from Col-0 accession at the same time point are indicated by * (P < 0.05).
Fig 7.
Accumulation of oxidants and superoxide dismutase (SOD) activity in response to salinity stress.
(A) Superoxide radical, detected by nitroblue tetrazolium (NBT) staining, (B) H2O2, detected by 3, 3’-diaminobenzidine (DAB) staining in Col-0 and the selected accessions exposed to 150 mM NaCl for 10 days. a: Col-0; b: Bs-1; c: Mog-11; d: Looe-2; e: Got-1; f: Wil-1; g: Nd-1; h: Sav-0. Bar = 0.1 cm. (C) SOD activity in Col-0 and the selected accessions exposed to 100 mM NaCl for 0, 3 and 9 h. Values given as mean ± SE (n = 3), each replicate comprised at least 15 seedlings. Significant differences from the performance of Col-0 accession at the same time point are indicated by * (P < 0.05).
Fig 8.
Expression analysis of genes related to ROS metabolism by qRT-PCR.
The transcript levels of (A) CSD1, (B) CAT2, (C) APX2, (D) ZAT10 and (E) ZAT12 in Col-0 and the selected accessions exposed to 100 mM NaCl for 0, 3 and 6 h. Significant differences from Col-0 accession at the same time point are indicated by * (P < 0.05).