Fig. 6.

Changes in growth, electrolyte leakage and proline contents of different genotypes under freezing condition. a, b Freezing assay of wild-type Col, soar1-2, soar1-3, and SOAR1-overexpression line (OE1). Two-week-old seedlings were placed directly under freezing condition (non-acclimated plants) at −4 °C (top, right in A, and NA −4 °C in B) or −6 °C (bottom, right in A, and NA −6 °C in B) for 1 h, while other two-week-old seedlings were firstly acclimated at 4 °C for 7 days and then placed under a freezing condition at −8 °C for 1 h (cold-acclimated plants, bottom, left in A, and CA −8 °C in B). The growth and survival rates of different genotypes were recorded after a 2-days recovery at 20 °C and are shown in A and B, respectively. The control plants were grown at 20 °C. Each value in B is the mean ± SE of three biological determinations and different letters indicate significant differences at P < 0.05 (Duncan’s multiple range test) within the same treatment. c Ion leakage of different genotypes described in A and B after freezing treatment. Each value is the mean ± SE of three independent determinations and different letters indicate significant differences at P < 0.05 (Duncan’s multiple range test) within the same treatment. (D) Proline content in different genotypes described in A. The plants were grown at 20 °C for 2 weeks, acclimated at 4 °C for 7 days, and sampled for analysis. Each value is the mean ± SE of three independent determinations and different letters indicate significant differences at P < 0.05 (Duncan’s multiple range test) within the same time point