Figure 1.

Hypocotyl elongation phenotype of Arabidopsis seedlings of wild type (Col-O) and four mutants (hot1–4). After growth for 2.5 days in the dark at 22°C, seedlings were either maintained at 22°C; treated at 38°C for 90 min; at 45°C for 2 h; or at 38°C for 90 min followed by 2 h at 22°C and then 45°C for 2 h. Seedlings were returned to 22°C for 2.5 days and then photographed. Groups of three seedlings that received the same treatment, as indicated above the panel, are shown. hot1, -2, and -4 seedlings are F₃ progeny of a single backcross to the wild-type parent. hot3 seedlings are from the M₃ generation, but show an identical phenotype to mutants segregating in the F₂ progeny of a backcross (not shown).