UV BAND FLUORESCENCE (IN-VIVO) AND ITS IMPLICATIONS FOR THE REMOTE ASSESSMENT OF NITROGEN SUPPLY IN VEGETATION

When excited at 280 nm, (intact vegetation produced two overlapping br oadband fluorescence emissions; the first centered near 335 nm [ultrav iolet (UV) band], and the second centered near 440 nm (blue band). Sep aration of these two fluorescence bands was achieved by an iterative n onlinear curve fit procedure utilizing the asymmetric double sigmoidal spectral function. The subsequent ratio of the deconvoluted curve int ensities exhibited a significant relation between protein concentratio n and fluorescence. UV band fluorescence from vegetation treated with varying levels of nitrogen fertilization decreased relative to the blu e fluorescence as a function of protein levels. These studies indicate that in vivo UV band fluorescence can be utilized as a nondestructive tool to remotely sense variations in protein concentration due to nit rogen supply. Strong similarities were noted in the UV band fluorescen ce characteristics of intact vegetation to both membrane-bound and sol uble plant proteins containing aromatic amino acids. Pure ribulose 1,5 -bisphosphate carboxylase in aqueous solution exhibited UV fluorescenc e characteristics with excitation and emission distributions similar t o those of intact vegetation. Because of its high concentration (up to 70% of the soluble leaf proteins), roe believe this protein contribut es to the UV band fluorescence emnnating from the intact leaf. In, add ition, similar fluorescence characteristics were observed for two othe r prominent enzymatic plant proteins; namely, adenosine 5'-tri-phospha tase and carboxylase phosphoenolpyruvate carboxcylase. These results i ndicate that UV band fluorescence emanating from the intact leaf could originate front several plant proteins that contain aromatic amino ac ids. (C) Elsevier Science Inc., 1997.