Figure 6.

Dependence on phytochrome of the blue-light-induced shrinking in wild-type protoplasts. The background red light was terminated at 20 min of incubation (see Fig. 1), and the protoplasts were subjected to various treatments (A–H described below; also illustrated), which included a dark period, a far-red-light pulse (3 min, 27 mmol m⁻²), and a red-light pulse (90 s, 4.5 mmol m⁻²). The protoplasts were then stimulated with a blue-light pulse (30 s, 3.45 mmol m⁻²), and background irradiation with red light was resumed. Time 0 represents the onset of blue-light stimulation. The volume of each protoplast at a given time was calculated as a percentage of the volume measured immediately after blue-light stimulation. The protoplasts that were initially in the volume range from 5 × 10³ to 30 × 10³ μm³ were analyzed. A through D, Protoplasts were stimulated with a blue-light pulse after pretreatments with a pulse of far-red light and a subsequent period of darkness; dark periods between the far-red-light and the blue-light pulse were 0 (A), 15 (B), 30 (C), and 60 (D) min. E through G, Protoplasts were stimulated with a blue-light pulse after pretreatments with a far-red-light pulse and a subsequent 60-min dark period interrupted with a red-light pulse. The dark intervals between the red-light and the blue-light pulse were 10 (E), 20 (F), and 30 (G) min. H, Protoplasts were treated with a red-light pulse as in G, but a pulse of far-red light was given immediately after the red-light pulse. The means ± se from 20 to 39 protoplasts are shown.