La. Corp et al., UV BAND FLUORESCENCE (IN-VIVO) AND ITS IMPLICATIONS FOR THE REMOTE ASSESSMENT OF NITROGEN SUPPLY IN VEGETATION, Remote sensing of environment, 61(1), 1997, pp. 110-117
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.