Freezing Tolerance of Mutants Involved in Jasmonate Biosynthesis and Signaling.
(A) Freezing phenotypes of MS medium–grown lox2, aos, and jar1 mutant plants with or without cold acclimation. Nonacclimated (NA) 12-d-old seedlings were treated at −4°C for 1 h, and cold-acclimated seedlings (2 weeks at 4°C) were exposed to −8°C for 1 h, followed by recovery at 22°C for 4 d. Experiments were performed three times with similar results. WT, the wild type.
(B) and (C) Survival rates of various nonacclimated (B) and cold-acclimated (C) mutant plants after exposure to indicated freezing temperatures. Error bars show sd from three replicates. CA, cold-acclimated (2 weeks at 4°C); MS, seedlings grown on MS medium; NA, nonacclimated.
(D) Ion leakage assays of mutants treated with indicated freezing temperatures. Error bars show sd from three replicates.
(E) Freezing phenotypes of coi1-1 and coi1-2 mutants with or without cold acclimation. Nonacclimated 12-d-old seedlings were treated at −4°C for 1 h, and cold-acclimated (2 weeks at 4°C) seedlings were exposed to −8°C for 1 h, followed by recovery at 22°C for 4 d. Experiments were performed three times with similar results.
(F) Freezing phenotypes of various soil-grown mutants with or without cold acclimation. Nonacclimated 18-d-old soil-grown seedlings were treated at −3 or −4°C for 1.5 h, and cold-acclimated seedlings (2 weeks at 4°C) were exposed to −7 or −8°C for 1.5 h, followed by recovery at 22°C for 7 d. Experiments were performed three times with similar results using over 100 plants per treatment.
(G) and (H) Survival rates of various nonacclimated (G) and cold-acclimated (H) soil-grown mutant plants after exposure to indicated freezing temperatures. Error bars show sd from three replicates. CA, cold-acclimated (2 weeks at 4°C); NA, nonacclimated; Soil, seedlings grown in soil. *Differences between the mutant and the wild type are significant (P < 0.05). **Differences between the mutant and the wild type are highly significant (P < 0.01).