Changes in cytosolic Ca²⁺ induced by BL in Arabidopsis etiolated seedlings. Aequorin luminescence is shown as the relative luminescence measured with the Auto Lumat LB9507 Luminometer. A and C, Changes in relative luminescence (RLU) indicate the changes in [Ca²⁺]_cyt in response to different intensities of BL or red light (RL). Etiolated seedlings of the wild type were irradiated with different intensities of BL for 15 s (A) and red light for 15 s (C). B and D, Mean changes in the cytosolic Ca²⁺ of A and C. E, The changes in relative luminescence in whole seedlings and hypocotyls were induced by irradiation with 100 μmol m⁻² s⁻¹  BL for 15 s. F, Mean changes in the cytosolic Ca²⁺ of E. Values are means of three independent experiments (seven to 21 measurements each) with sd.