Figure 1.

Changes in protoplast volume under background R and following a pulse of blue light. Protoplasts were prepared under R (2–3 μmol m⁻² s⁻¹) from the elongating stem zone of R-grown pea cv Alaska seedlings. The protoplasts were isolated from epidermal peels or the remaining peeled stems. The isolated protoplasts were bathed in a standard medium containing 0.5 m sorbitol, 10 mm KCl, 1 mm CaCl₂, 20 mm Glc, and 10 mm MES-KOH (pH 6.0). A 200-μL portion of freshly prepared protoplasts was added to an all-side clear cuvette and incubated under background R (50 μmol m⁻² s⁻¹) on the sample stage of an inverted microscope. During incubation the protoplasts were subjected to time-lapse photography to monitor their volume. The volume of each protoplast at a given time was calculated as a percentage of the volume at time 0, which corresponded to 40 min after the onset of incubation on the microscope stage. The protoplasts received no additional light treatment (A and C) or were irradiated with blue light (115 μmol m⁻² s⁻¹) for 30 s immediately after obtaining the photograph at time zero (B and D). The data shown are the means ± se obtained from more than 30 protoplasts.