Table 1.
Sequence of the primers used in this study.
Table 2.
The effect of different Cd concentrations on the biomass (dry weight) of the two maize varieties.
Fig 1.
Cd concentrations in the shoots (A) and roots (B) of two maize varieties. Data are presented as the treatment mean ± SD (n = 4). Different letters indicate significant differences at the P < 0.05 level (Duncan’s test). F-test: Cd concentration: Shoot: F(Cultivars) = 30.54**; F(Cd) = 134.57**; F(Cultivars × Cd) = 6.84**. Root: F(Cultivars) = 48.43**; F(Cd) = 489.93**; F(Cultivars × Cd) = 7.92**. *P < 0.05; **P < 0.01.
Fig 2.
Effects of different Cd concentrations on the (A) photosynthetic rate, chlorophyll (B) a and (C) b contents of the two maize varieties. Data are presented as the treatment means ± SD (n = 4). Different letters indicate a significant difference when P < 0.05 (Duncan’s test). F-test: Photosynthetic rate: F(Cultivars) = 55.54**; F(Cd) = 102.15**; F(Cultivars × Cd) = 0.41. Chlorophyll a: F(Cultivars) = 17.11**; F(Cd) = 80.63**; F(Cultivars × Cd) = 2.36. Chlorophyll b: F(Cultivars) = 39.60**; F(Cd) = 181.13**; F(Cultivars × Cd) = 2.63. *P < 0.05; **P < 0.01.
Fig 3.
Soluble sugar contents in (A) shoots and (B) roots, sucrose contents in (C) shoots and (D) roots, glucose contents in (E) shoots and (F) roots, and fructose contents in (G) shoots and (H) roots of two maize varieties with different concentrations of Cd. Data are presented as the treatment means ± SD (n = 4). Different letters indicate a significant difference when P < 0.05 (Duncan’s test). F-test: Soluble sugar: Shoot: F(Cultivars) = 41.95**; F(Cd) = 72.32**; F(Cultivars × Cd) = 14.59**. Root: F(Cultivars) = 0.11; F(Cd) = 104.95**; F(Cultivars × Cd) = 19.10**. Sucrose: Shoot: F(Cultivars) = 39.99**; F(Cd) = 12.32**; F(Cultivars × Cd) = 7.92**. Root: F(Cultivars) = 298.49**; F(Cd) = 4.58*; F(Cultivars × Cd) = 5.19*. Glucose: Shoot: F(Cultivars) = 56.02**; F(Cd) = 9.93**; F(Cultivars × Cd) = 1.31. Root: F(Cultivars) = 219.45**; F(Cd) = 3.39*; F(Cultivars × Cd) = 3.84*. Fructose: Shoot: F(Cultivars) = 131.27**; F(Cd) = 58.23**; F(Cultivars × Cd) = 32.67**. Root: F(Cultivars) = 0.59; F(Cd) = 2.88; F(Cultivars × Cd) = 3.52*. *P < 0.05; **P < 0.01.
Fig 4.
Sucrose phosphate synthase (SPS) activity in (A) shoots and (B) roots, acid invertase (AI) activity in (C) shoots and (D) roots, sucrose synthase (SS) hydrolysis activity in (E) shoots and (F) roots, and SS synthesis activity in (G) shoots and (H) roots of two maize varieties at different concentrations of Cd. Data are presented as treatments mean ± SD (n = 4). Different letters indicate a significant difference when P < 0.05 (Duncan’s test). F-test: SPS activity: Shoot: F(Cultivars) = 33.28**; F(Cd) = 137.86**; F(Cultivars × Cd) = 3.95*. Root: F(Cultivars) = 3.54; F(Cd) = 69.3**; F(Cultivars × Cd) = 1.03. AI activity: Shoot: F(Cultivars) = 105.07**; F(Cd) = 105.5**; F(Cultivars × Cd) = 6.1**. Root: F(Cultivars) = 2.3; F(Cd) = 4.61*; F(Cultivars × Cd) = 2.59. SS-H activity: Shoot: F(Cultivars) = 7.51*; F(Cd) = 12.93**; F(Cultivars × Cd) = 2.78. Root: F(Cultivars) = 0.47; F(Cd) = 6.19**; F(Cultivars × Cd) = 4.09*. SS-S activity: Shoot: F(Cultivars) = 126.42**; F(Cd) = 15.18**; F(Cultivars × Cd) = 7.84**. Root: F(Cultivars) = 1.89; F(Cd) = 62.31**; F(Cultivars × Cd) = 1.04. *P < 0.05; **P < 0.01.
Fig 5.
Expression profiles of three SWEET13 genes in (A) the shoots of FY9, (B) in the shoots of SY33, (C) in the roots of FY9, and (D) in the roots of SY33 under different Cd concentration treatments (blue: 0 mg L−1; orange: 5 mg L−1; gray: 10 mg L−1; yellow: 20 mg L−1). Data are presented as treatment means ± SD (n = 3). Different letters indicate a significant difference when P < 0.05 (Duncan’s test).
Fig 6.
Expression profiles of two SUT genes in (A) the shoots of FY9, (B) the shoots of SY33, (C) the roots of FY9, and (D) the roots of SY33 at different Cd concentration treatments (blue: 0 mg L−1; orange: 5 mg L−1; gray: 10 mg L−1; yellow: 20 mg L−1). Data are presented as the treatment means ± SD (n = 3). Different letters indicate significant difference when P < 0.05 (Duncan’s test).