Figure 6.

Low irradiances increase the number of small phyB-NBs even under low R:FR. A, Response of phyB-NBs under natural radiation. Plants were grown under natural photoperiods (14-h light, 10-h darkness) during early summer in Buenos Aires. At midday of day 15, plants were left as high-irradiance and high-R:FR controls under unfiltered sunlight (1,360 µmol m^–2 s^–1 of photosynthetically active radiation, R:FR = 1.2) or transferred to either low R:FR (1,360 µmol m^–2 s^–1 photosynthetically active radiation plus supplementary far-red light, R:FR = 0.8) or low irradiance and low R:FR under the natural shade provided by a canopy of Tipuana tipu trees (110 µmol m^–2 s^–1 photosynthetically active radiation, R:FR = 0.8). Confocal images were taken 2 h later. B, Response of phyB-NBs under controlled conditions. Plants were grown at high irradiance and high R:FR (200 µmol m^–2 s^–1 photosynthetically active radiation, R:FR = 4.3). At 4 h of the photoperiod, plants were left as controls or transferred to either high irradiance and low R:FR (0.8) or low irradiance and low R:FR (25 µmol m^–2 s^–1 photosynthetically active radiation, R:FR = 0.8). Confocal images were taken 2 h later. C, Representative confocal images showing nuclei under controlled light conditions. Bar = 5 µm. Data are means ± se of three plants. Different letters denote significant differences among means (P < 0.05) in ANOVA followed by Bonferroni posttests. [See online article for color version of this figure.]