DETERMINATION OF THE EFFECT OF DIRECTED LIGHTING BY BLUE LIGHT-EMITTING DIODES ON GROWTH OF TAP ROOTS OF ARABIDOPSIS THALIANA SEEDLINGS DURING SLOW 2D-CLINOSTAT ROTATION

The paper presents the results of experiments with 48-hour horizontal and vertical clinostatting of 5-day old Arabidopsis thaliana seedlings in 2 types of lighting, i.e. white light (4000 cd) and lateral blue light (450 nm). The experiments were performed in a clinostat designed to install Petri dishes with juvenile Arabidopsis thaliana in the horizontal and rotate it about the horizontal axis at a speed of 1 rev/min. Angular bend of the main root (MR) was measured as it elongated. It was demonstrated that, on the average, vertical clinostating in white light caused a more significant MR departure from the apical-basis axis than the horizontal clinostating. The proposed space experiments with Arabidopsis seedlings and laboratory controls will require extensive preliminary studies of the effects of specific light spectra and directions, and crop orientation. In blue light, there was no difference in the MR departure due to the seedlings placement in the clinostat; however, more than 75 % of the seedlings tended to bend away from the light source. Directed blue lighting in a 2D-clinostat can be an approach to root system orientation based on the negative phototropism.