PNNL-13501 - Pacific Northwest National Laboratory

- 3
1 4 x 1 0
Relative Intensity
1 2
1 0
8
6
4
2
0
0 1 0 0 0 2 0 0 0 3 0 0 0 4 0 0 0 5 0 0 0 6 0 0 0
D i s t a n c e f r o m R o o t T i p ( µ m )
Figure 3. Fluorescence levels at 394 nm along longitudinal
axis of oat root immersed in 10 mM europium (III) for 48
hours
Observations also indicate a preferential abaxial
distribution of the europium (III) parallel to the plane of
gravity. This may indicate regions where there are high
extracellular fluxes of Ca +3 in response to gravitropic
stimulation. Calcium fluxes are important to nutrition and
other metabolic activities. If europium (III) is an effective
calcium probe, possible in vivo observations of plant
nutrition activities are possible. Also europium (III)
fluorescence was often higher in cells with dense
cytoplasm and high nucleic acid to cytoplasm ratios
(meristematic and phloem cells). Uranium, another
actinide, is often used as a nucleic acid stain in electron
microscopy. Europium interaction with similar material
may permit real-time analysis of the effects of the
actinides on cellular metabolism.
Summary and Conclusions
The results of this work show a new technique for the in
vivo, real-time study of metal europium (III)
Media
Epidermis
Cortex
Endodermis
St Parenchyma
Xy Parenchyma 0
Protoxylem
Metaxylem
Sieve Element-
Companion Cell Complex
86 FY 2000 Laboratory Directed Research and Development Annual Report
3
2
1
accumulation by a functioning intact plant root. Highest
concentations were observed in the stele of the root,
specifically in the xylem parenchyma and phloem. This
approach can prove valuable for basic and applied studies
in plant nutrition and environmental uptake of actinide
radionuclides, as well as micronutrient metals.
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M e d i a E p i d e r m i s C o r t e x E n d o d e r m i s S t e l a r D e v e l o p i n g
P a r e n c h . M e t a x y l e m
C e l l T y p e
C o m p a n i o n
C e l l S i e v e
E l e m e n t
X y l e m P r o t o x y l e m
P a r e n c h .
Figure 4. Micrograph of oat root cross section identifying cell types within root and graph giving the relative fluorence at 394 nm