Figure 3.

siz1-2 and siz1-3 seedlings exhibit reduced basal thermotolerance but not acquired thermotolerance. A, Ten-day-old wild-type, siz1 (siz1-2 and siz1-3), NahG siz1-2, NahG, and hot1-3 seedlings were not acclimated (normal, 22°C) or high-temperature acclimated by exposure to 39°C for 90 min. After a recovery period of 2 h at 22°C, seedlings were exposed to a heat shock of 45°C for 2 h under the conditions described in the Figure 1 legend. Illustrated are representative seedlings 4 d after heat shock treatment. B, Stratified seeds of genotypes described in A were incubated in the dark at 22°C/18°C (16 h/8 h). Three days thereafter, seedlings were high-temperature acclimated by exposure to 39°C for 90 min. After a recovery period of 2 h at 22°C, seedlings were exposed to a heat shock of 45°C for 2 h under conditions described in the Figure 1 legend and then grown for 2.5 d at 22°C/18°C (16 h/8 h). Illustrated are relative growth determinations (100% indicates the growth of genotypes at 22°C) from three independent experiments, mean ± se, n ≥ 18 seedlings/experiment.