Antioxidant enzyme activities of <i>G. parviflora</i> in the pot experiment.

<p>Superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) activities were measured in plants cultured for 50 d in soil containing 10 mg added Cd (kg soil)⁻¹. Values are means (±SE) of three replicate pots. Different lowercase letters within a column indicate significant differences based on one-way analysis of variance in SPSS 13.0 followed by the least significant difference test (<i>P</i><0.05).</p><p>Antioxidant enzyme activities of <i>G. parviflora</i> in the pot experiment.</p

Cadmium extraction by <i>G. parviflora</i> in the pot experiment.

<p>Plants were cultured in soil containing 40 mg added Cd (kg soil)⁻¹ for 50 d. Values are means (±SE) of three replicate pots. Different lowercase letters within a column indicate significant differences based on one-way analysis of variance in SPSS 13.0 followed by the least significant difference test (<i>P</i><0.05). Translocation accumulation factor (TAF) = (Cd content in shoot×shoot biomass)/Cd content in root×root biomass.</p><p>Cadmium extraction by <i>G. parviflora</i> in the pot experiment.</p

Height of <i>G. parviflora</i> plants in the pot experiment.

<p>Plants were cultured in soil containing 10 mg added Cd (kg soil)⁻¹ for 50 d. Values are means of three replicate pots. Different lowercase letters indicate significant differences based on one-way analysis of variance in SPSS 13.0 followed by the least significant difference test (<i>P</i><0.05). CK = control, R.S = <i>Ranunculus sieboldii</i>, C.C = <i>Clinopodium confine</i>, M.J = <i>Mazus japonicus</i>, P.A = <i>Plantago asiatica</i>.</p

Cadmium content in <i>G. parviflora</i> in the pot experiment.

<p>Plants were cultured in soil containing 10 mg added Cd (kg soil)⁻¹ for 50 d. Values are means (±SE) of three replicate pots. Different lowercase letters within a column indicate significant differences based on one-way analysis of variance in SPSS 13.0 followed by the least significant difference test (<i>P</i><0.05). The translocation factor (TF) is defined as Cd content in shoot/Cd content in root and the shoot bioconcentration factor (BCF) is defined as Cd content in shoot/Cd concentration in soil.</p><p>Cadmium content in <i>G. parviflora</i> in the pot experiment.</p

Biomass and cadmium accumulation in the field experiment.

<p>Plants were cultured in soil containing 1.8 mg added Cd (kg soil)⁻¹ for 60 d in a field experiment. Values are means (±SE) of three replicate plots. Different lowercase letters within a column indicate significant differences based on one-way analysis of variance in SPSS 13.0 followed by the least significant difference test (<i>P</i><0.05).</p><p>Biomass and cadmium accumulation in the field experiment.</p

Relative expression levels of sugar metabolism-related genes in peach fruits.

Values represent the mean ± SD (n = 3). Asterisks indicate significant differences between the treatments using the Student’s t-test (*: 0.01 ≤ p p A: sucrose synthase (SS), B: sucrose phosphate synthase (SPS), C: neutral invertase (NI), D: acidic invertase (AI), and E: sorbitol dehydrogenase (SDH) genes.</p

Relative expression levels of organic acid metabolism-related genes in peach fruits.

Values represent the mean ± SD (n = 3). Asterisks indicate significant differences between the treatments using the Student’s t-test (*: 0.01 ≤ p p A: NADP+-malic enzyme (NADPME), B: malate dehydrogenase (MDH), C: citrate synthetase (CS), D: phosphoenolpyruvate carboxylase (PEPC), and E: aconitase (ACO) genes.</p

Organic acid contents in peach fruits.

Values represent the mean ± SD (n = 3). Asterisks indicate significant differences between the treatments using the Student’s t-test (*: 0.01 ≤ p p A: total acid content; B: malic acid content; C: citric acid content.</p

Fig 2 -

Activities of the sugar metabolism-related enzymes in peach fruits. Values represent the mean ± SD (n = 3). Asterisks indicate significant differences between the treatments using the Student’s t-test (*: 0.01 ≤ p p A: sucrose synthase (SS) activity; B: sucrose phosphate synthase (SPS) activity; C: neutral invertase (NI) activity; D: acidic invertase (AI) activity; E: sorbitol dehydrogenase (SDH) activity; F: sorbitol oxidase (SOX) activity.</p

S1 Data -

To evaluated the effects melatonin (MT) on the sugar and acid metabolism of early-ripening peach fruits, the concentration of 150 μmol/L MT was sprayed on the leaves of peach trees. MT increased the contents of total soluble sugar and sucrose in peach fruits during the whole ripening period, and increased the contents of glucose and sorbitol at the mature stage. During the whole ripening period, MT also increased the activities of sucrose synthase, sucrose phosphate synthase, neutral invertase, and acidic invertase and the relative expression levels of sucrose synthase, sucrose phosphate synthase, neutral invertase, and acidic invertase genes, while decreased the activity of sorbitol oxidase and the relative expression level of sorbitol dehydrogenase to some extent. Moreover, MT decreased the contents of total organic acid, malic acid, and citric acid at mature stage. At mature stage, MT decreased the activities of citrate synthetase and phosphoenolpyruvate carboxylase and the relative expression levels of citrate synthetase and phosphoenolpyruvate carboxylase genes, while increased the relative expression levels of Nicotinamide adenine dinucleotide phosphate (NADP+)-malic enzyme, malate dehydrogenase, and aconitase genes. Therefore, MT promotes the sugar accumulation and organic acid degradation in early-ripening peach fruits.</div