Figure 2.

Phytochrome regulation of the blue light-sensitive shrinking response in epidermal protoplasts. Protoplasts isolated from epidermal peels of pea cv Alaska seedlings were set on the microscope stage and incubated under background R as described for Figure 1. The R was turned off after 10 min of incubation and the protoplasts were subjected to different 30-min treatments that included darkness, a 3-min pulse of FR (150 μmol m⁻² s⁻¹), and a 90-s pulse of R (50 μmol m⁻² s⁻¹). Following the 30-min treatment period, background R irradiation was resumed, time-lapse photography for volume determination was initiated, and the protoplasts were treated with a 30-s pulse of blue light (115 μmol m⁻² s⁻¹). The onset of R, the first photograph at time zero, and the onset of blue light were within a few seconds of each other. The treatment protocol is illustrated in each panel, with the black bar representing darkness. The volume of each protoplast was calculated as a percentage of the volume at time zero, the time at which the first photograph was obtained. The means ± se from 21 to 25 protoplasts are shown.