Changes of spectral characteristics of the reflectance and luminescence spectra of barly leaves under clinorotation

The aim of the work was to study the effect of imitated weightlessness (horisontal clinorotation at 4 rpm) on the characteristics of the reflectance and luminescence spectra of barly leaves. The leaves of one week and two week old plants was used for the investigation. Reflectance spectra were registered with the help of spectrometer SF-18 (LOMO, USSR). Spectra of luminescence were registered by using the installation assembled in the laboratory. Luminescence was excitated by nitrogen laser with a wavelength of radiation 337,2 nm. The impulse recording system was realized with the using of special detectors. The red (650-750 nm) and the blue -green (400-550 nm) luminescence was registered with spectral resolution 1 nm. The luminescence and reflectance data noted in an analog and digital kind for their further processing with the help of the appropriate algorithms.The effect of two week clinorotation has manifested in increase of reflectance in the green region with the maximum at 550 nm and in the changes of the spectral curve form in the region of so-called "red edge"(680-740nm). Quantitatively, these changes were consisted in the short-wavelength shift of the minimum reflectance and in the decreasing of the ratio of amplitude maxima of the first derivative from the reflectance spectral curve (dR/d λ) ₇₁₅/(dR/d λ) ₆₈₅. This changes as more high reflectance at 550 nm, evidenced about reduced chlorophyll content in the leaves. In the luminescence spectra the changes induced by clinorotation refer to both red and blue-green luminescence. For young leaves, the ratio between long-wave and short-wave maxima of the red luminescence was higher compared to the control. Further this ratio showed a tendency toward the decrease as a result of chlorophyll decreasing in the leaves. In the blue-green region there took place an increase of the relative intensity of the green luminescence with maximum 530 nm in comparison with 430 or 450 nm. The observable increase reached 25%. According to literature data the ratio F 530/F450 is informative parameter in relation to ratio between carotenoids and chlorophylls content in leaves. It increase may be testify to more high carotenoids content in the leaves of clinorotated plants. It has been found that the effect of clinorotation on the measured parameters was more visible in plants grown at low light intensity.