Figure 4.

Stress tolerance of transgenic tobacco plants expressing constitutively active NPK1. (A) Normal vegetative growth of NPK1 plants. Wild-type (WT) and transgenic (2A, 3B, 4A) plants were germinated and grown on a ¼× MS medium for 3 weeks. (B) Tolerance to freezing temperature. Plants were grown on plates for 10 days before freezing temperature treatment (−10°C, 3 h). The photograph was taken 11 days after the treatment. (C) Tolerance to heat shock. Plants were grown for 10 days before heat treatment (48°C, 45 min). The photograph was taken 18 days after the treatment. (D) Tolerance to salt stress. Plants were grown for 6 days and then transferred to plates containing 300 mM NaCl for 3 days. The photograph was taken 11 days after the plants were returned to ¼× MS medium plates. The graphic data are results of 50 plants of each genotype for C and D.