Flowering initiation in carrots by tailoring the illumination spectrum

The present study was based on the investigation of the influence of illumination spectrum on physiological processes in carrots (Daucus carota L.) during their evocation, flower initiation and differentiation. The process of carrot flower initiation and morphogenesis was studied in a phytotron facility under treatment with different illumination spectra provided by an illuminator based on light-emitting diodes (LEDs) and a reference illuminator based on high-pressure sodium lamps. High-performance liquid chromatography (HPLC) was used for detection and separation of phytohormones (cytokinin, gibberellins, indol-3-acetic acid, and abscisic acid). A considerable influence of illumination spectrum on physiological processes in carrot, especially on morphogenesis rate during evocation, flower initiation and differentiation, was observed. We demonstrate that the plants are more sensitive to the photon flux density and the illumination spectrum during flower initiation and differentiation. An increase of the photon flux was shown to stimulate the synthesis of gibberellic acid, zeatin and indolyl-3-acetic acid in carrots during the evocation, flower initiation and differentiation processes. Meanwhile, the concentration of abscisic acid simultaneously decreased. Thus, the flower initiation processes in carrots can be controlled by treatment with different illumination spectrum and photon flux density tailored by using LEDs. This enables one to accelerate plant cultivation in phytotron conditions.