Fig. 6.

Oxidative stress and short term freezing tolerance of wild type (WT) and transgenic tobacco plants (S13, S15). (a) Leaf disks were incubated in different concentration of H₂O₂ (1% and 2%, respectively) under continuous white light for 72 h. H₂O₂ induced leaf yellowing is delayed in the transgenic plants. (b) Three-week-old seedlings were stored at −20°C for 2 h, and then transferred to normal temperature for further growth. Photograph was taken seven days after the freezing treatment. (c) Quantification of the seedling survival rate (determined seven days after the freezing treatment). Results are presented as means and standard errors from three independent experiments. Fore each experiment, 40 seedlings of each line were used. *** indicates significant difference in comparison to the wild type at P < 0.001 (Student’s t-test). (d) Chlorophyll content was determined in leaf disks of wild type and T₂ transgenic plants kept in H₂O₂ for 72 h. Disks floated in water served as control. Results are preans and standard errors from three independent experiments. ** and *** indicate significant differences in comparison to the wild type at P < 0.01 and P < 0.001, respectively (Student’s t-test)