Seeds of the Columbia (Col-0) ecotype of Arabidopsis were obtained from Lehle Seeds (Round Rock, Texas). Plants were grown on 1 Murashige and Skoog medium from Caisson labs (North Logan, Utah) pH 5.7, 0.8% (w/v) agar, and supplemented with 1% (w/ v) sucrose. After cold treatment for 48 h at 4 C, plates were moved to a growth chamber and grown under 100 lmol m2 s 2 coolwhite light (24 h lighting). The growth chamber was maintained at 22 C and 60% relative humidity. All assays were conducted 5 d after germination, which was typically 6–7 d after the cold treatment.4.2