PLANT PHYSIOLOGY , Vol 106, Issue 1 127-133, Copyright © 1994 by American Society of Plant Biologists
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ENVIRONMENTAL AND STRESS PHYSIOLOGY |
Characterization of Blue-Green Fluorescence in the Mesophyll of Sugar Beet (Beta vulgaris L.) Leaves Affected by Iron Deficiency
F. Morales, Z. G. Cerovic and I. Moya
Laboratoire pour I'Utilisation du Rayonnement Electromagnetique, Universite de Paris XI, 91405 Orsay, France
The mesophyll of sugar beet (Beta vulgaris L.) leaves emits red
(chlorophyll a) fluorescence and blue-green fluorescence when excited with
ultraviolet light. The intensity of blue-green fluorescence was increased
in mesophylls affected by iron deficiency. This increase was large and
progressive. It was concomitant with a decrease of photosynthetic pigments
per unit of leaf area. Most of the increase in blue-green fluorescence can
be explained by the decrease of the screening of ultraviolet light by
chlorophylls and carotenoids. In addition, chlorophylls selectively
reabsorb blue fluorescence, which leads to a change in the form of the
fluorescence emission spectra. This effect induces an increase of the
blue-to-green fluorescence ratio in control mesophylls that was concomitant
with the decrease of chlorophyll per unit of leaf area. Iron deficiency
induced a decrease of the blue-to-green fluorescence ratio that may be
attributed to an accumulation of flavins fluorescing in the green.
Time-resolved fluorescence measurements indicate that they are mostly
riboflavin and/or flavin mononucleotide phosphate. Our data also indicate
that the blue-green fluorescence emitted from the mesophyll contains
fluorescence of nicotinamide nucleotides.
