Multicolour fluorescence imaging of sugar beet leaves with different nitrogen status by flash lamp UV-excitation

Fluorescence images of leaves of sugar beet plants (Beta vulgaris L. cv. Pa tricia) grown on an experimental field with different fertilisation doses o f nitrogen [0, 3, 6, 9, 12, 15 g(N) m(-2)] were taken, applying a new multi colour flash-lamp fluorescence imaging system (FL-FIS). Fluorescence was ex cited by the UV-range (280-400 nm, lambda (max) = 340 nm) of a pulsed Xenon lamp. The images were acquired successively in the four fluorescence bands of leaves near 440, 520, 690, and 740 nm (F-440, F-520, F-690, F-740) by m eans of a CCD-camera. Parallel measurements were performed to characterise the physiological state of the leaves (nitrogen content, invert-sugars, chl orophylls and carotenoids as well as chlorophyll fluorescence induction kin etics and beet yield). The fluorescence images indicated a differential loc al patchiness across the leaf blade for the four fluorescence bands. The bl ue (F-440) and green fluorescences (F-520) were high in the leaf veins, whe reas the red (F-690) and far-red (F-740) chlorophyll (Chl) fluorescences we re more pronounced in the intercostal leaf areas. Sugar beet plants with hi gh N supply could be distinguished from beet plants with low N supply by lo wer values of F-440/F-690 and F-440/F-740. Both the blue-green fluorescence and the Chi fluorescence rose at a higher N application. This increase was more pronounced for the Chi fluorescence than for the blue-green one. The results demonstrate that fluorescence ratio imaging of leaves can be applie d for a non-destructive monitoring of differences in nitrogen supply. The F L-FIS is a valuable diagnostic tool for screening site-specific differences in N-availability which is required for precision farming.