Chemical Composition of Tobacco Leaves Altered by Near-Ultraviolet and Intensity of Visible Light

Abstract

Low energies of near-ultraviolet radiation (300-400 nano- meters), applied simultaneously with visible radiation to Nicotiana tabacum L. during daily illumination periods, in- creased levels of chlorogenic acid isomers, total soluble phe- nolics, alkaloids, and soluble sugars in expanding leaf lamina compared with controls that had near-ultraviolet filtered out. However, total nitrogen concentrations decreased. The re- sponses to near-ultraviolet were interrelated with intensity of visible light. The presence of near-ultraviolet (which accounted for less than 4% of the total light energy) along with visible light resulted in component concentration differences similar to those caused by much greater increases of visible light without near-ultraviolet.