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Figure 1. 

Effects of temperature on the germination of different varieties of melon seeds. (a) Germination percentage and (b) relative GI, VI, radicle length and bud fresh weight. The seeds were subjected to 28 °C or 15 °C incubator for germination. The germination percentage was counted at 0, 24 and 36 h at 28 °C or L0, L84 and L108 h at 15 °C and R24 at 28 °C. The relative GI, VI, radicle length and bud fresh weight were calculated based on the ratio of these indexes at L108 (15 °C) and R24 h (28 °C). Data were presented as means of three biological replicates ± standard error, and * indicate significant differences at p < 0.05 according to Tukey's test.

Figure 2. 

Effects of temperature on the contents of starch and soluble sugar in different varieties of melon seeds. (a) Starch content and (b) soluble sugar content. The seeds were subject to 28 °C or 15 °C incubator for germination. The contents of starch and soluble sugar were determined at 0, 12, 18, 24 and 36 h at 28 °C or L0, L36, L60, L84 and L108 h at 15 °C and R24 h at 28 °C. Data were presented as means of three biological replicates ± standard error, and * indicate significant differences at p < 0.05 according to Tukey's test.

Figure 3. 

Effects of temperature on the contents of Suc, Glu and Fru in different varieties of melon seeds. The seeds were subject to 28 °C or 15 °C incubator for germination. The contents of Suc, Glu and Fru were determined at 0, 24 and 36 h at 28 °C or L0, L36, L84 at 15 °C and R24 h at 28 °C. Data were presented as means of three biological replicates ± standard error, and * indicate significant differences at p < 0.05 according to Tukey's test.

Figure 4. 

Effects of temperature on the activities of NI and AI in different varieties of melon seeds. The seeds were subject to 28 °C or 15 °C incubator for germination. The activities of NI and AI were determined at 0, 24 and 36 h at 28 °C or L0, L36, L84 at 15 °C and R24 h at 28 °C. Data were presented as means of three biological replicates ± standard error, and * indicate significant differences at p < 0.05 according to Tukey's test.

Figure 5. 

Effects of temperature on the genes expression of CmNIs in different varieties of melon seeds. The seeds were subject to 28 °C or 15 °C incubator for germination. The gene expression of NI were determined at 0, 12, 24 and 36 h at 28 °C or L0, L36, L60, L84 at 15 °C and R24 h at 28 °C. The CmNIs levels in the THY seeds at 0 h were normalised as 1. Data were presented as means of three biological replicates ± standard error, and * indicate significant differences at p < 0.05 according to Tukey's test.

Figure 6. 

Effects of Suc and Glu on germination percentage of different varieties of melon seeds under normal or low temperature. The seeds were pre-soaked in 50 mM Suc or 20 mM Glu solutions for 6 h, followed by rinsing with double-distilled water (ddH₂O). Seeds were subjected to 28 °C or 15 °C incubation for germination. The germination percentage was counted at (a) 36 h at 28 °C or (b) L108 h at 15 °C and R24 at 28 °C, and (c) the photos of seeds germination were taken. Data were presented as means of three biological replicates ± standard error, and * indicate significant differences at p < 0.05 according to Tukey's test.

Figure 7. 

Contents of ABA and GAs (GA9, GA15 and GA53) in different varieties of melon seeds under L108 h. The seeds were subject to 15 °C incubator for germination. The contents of ABA and GAs were determined at L108 h under 15 °C. Data were presented as means of three biological replicates ± standard error, and * indicate significant differences at p < 0.05 according to Tukey's test.