Transcript Carbon Isotope Fractionation within Plants

Carbon Fractionation within
Individual Plants
MEAS 760
Lori Skidmore & Jonathon Harris
C13 within Plants
• Does C13 vary within individual plants?
• Is there a difference in internal
fractionation between C3 and C4 plants?
• Many studies examining effects of C4
metabolism:
– Winkler et al. 1978
– Farquhar et al. 1983
– Hobbie and Werner 2004
• Prairie Ridge Data Summary
Does C13 vary within plants?
• YES!
• Carbon fractionation within plants can be
described by differences in:
– Plant organs
– Plant compounds
Fractionation in Plant Organs
• Differences in bulk d13C of different plant
parts (leaves, roots) are common.
• Since most d13C measurements are made
on leaves, it is important to indicate the
plant part measured.
• Fractionation in plant organs differs among
C3 and C4 plants (see figure on next
slide).
(From Hobbie and Werner, 2003)
Root to shoot variation
Table 3 Werth & Kuzyakov 2006
• Roots are slightly depleted in heavier isotope,
compared to shoots but not when compared to
leaves.
Organs: C3 versus C4
C3 Plants
• Roots are typically
enriched by 1–3‰
relative to leaves.
• Grains enriched by 1–
4‰ relative to leaves.
C4 Plants
• Roots similar or
slightly lower in δ13C
relative to leaves.
• Grains enriched by ≈
1.5‰ relative to
leaves in maize.
(Hobbie and Werner, 2003)
Fractionation in Plant Compounds
• Variations in the isotopic
composition of plant organs
can be shown to correspond
to isotopic differences
between organic compounds
in the plant.
• Figure shows carbon isotope
fractionation between aminoacids in Chlorella pyrenoides
(Abelson and Hoering,
1961).
Fractionation in Plant Compounds
• Hobbie & Werner 2004
– Suggest early isotopic fractionation in
derivatives of photosynthesis lead to large
differences later on.
– If HCO3- becomes enriched in dC13 early on in
C4 metabolism all of the later derivatives of that
molecule will show the signs of that early
discrimination.
– Plant tissues higher in certain compounds than
other tissues such as lignin or certain waxes will
then reflect this on a plant wide level.
Fractionation in Plant Compounds
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•
•
•
Reactions and transport
processes affect composition of
compounds in different plant
tissues.
Movement and isotopic
fractionation of carbon between
leaves and roots results in 13Cdepleted products and 13C
enrichment in residuals
Isotopic depletion of lignin and
lipids depends on the fraction (f )
of available substrate
transformed to lignin and lipids
and the isotopic fractionation (∆)
of the reaction.
(Hobbie and Werner, 2003).
Compounds: C3 versus C4
C3 Plants
• Alkanes and lipids 4–6‰
depleted (Collister et al.,
1994).
C4 Plants
• Alkanes and lipids 8–
10‰ depleted (Collister
et al., 1994).
• In C4 plants, lipid
concentration was found
to be about half that in C3
plants (Chikaraishi and
Naraoka, 2001).
• Isotopic enrichment of
cellulose relative to lignin
is slightly greater in
leaves of C4 plants.
Prairie Ridge Results
BROADLEAF PLANTS
Plant type
Plant name
C3
Ambrosia artemisiifolia
(Ragweed)
Sample ID
Leaf
PRP-3
-31.53
PRP-4
-31.61
Flower
-30.72
Stem
Root
-31.91
-18.82
-30.12
-16.1
-28.37
-27.5
Stem
Root
-30.73
Solanaceae carolinense
PRP-8
-30.29
C3
(Horsenettle)
GRASSES
Plant type
Plant name
Sample ID
Green blade
Brown blade
Festuca
(Fescue)
PRP-9
-29.35
-29.9
-25.6
C3
-28.63
-26.01
C4
PRP-12
PRP-6
-13.28
-13.58
-12.41
-28.73
PRP-11
-12.47
-13.6
-12.94
-12.48
Cynodon dactyla
(Bermuda grass)
-13.63
PRP-13
PRP-14
-13.82
-13.89
-13.17
-14.43
Results: Broadleaf plants
Average d13C (%o)
Ragweed
[*Part* d13C – Leaf d13C]
• Ragweed
–
–
–
–
Leaf = -31.57
Flower = -30.73 [ +0.845]
Stem = -31.02 [ +0.555]
Root = -17.46 [ +14.11]
• Horsenettle
Horsenettle
– Leaf = -30.29
– Stem = -28.37 [+1.92]
– Root = -27.50 [ +2.79]
Results: Grasses
Average d13C (%o)
Fescue
[*Part* d13C – Green blade d13C]
• Bermuda grass
–
–
–
–
Green blade = -13.21
Brown blade = -13.56 [ -0.347]
Stem = -13.26 [-0.047]
Root = -12.48 [+0.733]
• Fescue
Bermuda grass
– Green blade = -29.35
– Brown blade = -29.27 [+0.085]
– Root = -25.81 [+3.545]
Conclusions
• Isotopic composition can vary by:
– Plant organ measured
– Plant organic compound measured
• Degree of fractionation variable among C3
and C4 plants
• Variations in plant organ d13C correspond
to isotopic variations in plant organic
compounds (metabolites).
Conclusions: Prairie Ridge
• Roots enriched relative to leaves in C3 and C4
plants.
– Isotopic fractionation greater within C3 plants
– Isotopic fractionation greater in broadleaf plants than
grasses
• Bermuda grass root data too varied to reliably
describe behavior.
• Ragweed exhibited greatest variation between
roots (-17.46 %o) and leaves (-31.57 %o)
Differences in Prairie Ridge Data
• Differences between different plant groups
• Perhaps different compound abundances
in Cynodon dactlyon roots than in Zea
maize roots
• Sample preparation flawed (Bermuda
grass root samples?!?)
REFERENCES
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Abelson, P.H. and T.C. Hoering. 1961. Carbon isotope fractionation in
formation of aminoacids by photosynthetic organisms. Biogeochemistry, 47:
623-632.
Chikaraishi Y, Naraoka H. 2001. Organic hydrogen–carbon isotope
signatures of terrestrial higher plants during biosynthesis for distinctive
photosynthetic pathways. Geochemical Journal 35: 451–458.
Collister JW, Rieley G, Stern B, Eglinton G, Fry B. 1994. Compound specific
d13C analyses of leaf lipids from plants with differing carbon dioxide
metabolisms. Organic Geochemistry 21: 619–627.
Hillaire-Marcel, G. 1986. Isotopes and Food in Handbook of Environmental
Isotope Geochemistry, Volume 2. The Terrestrial Environment, B. (Eds. P.
Fritz and J.C. Fontes). Elservier Science Publishers, Amsterdam. Chapter
12, p. 507-548.
Hobbie, E.A. and R.A. Werner. 2004. Intramolecular, compound-specific,
and bulk carbon isotope patterns in C3 and C4 plants: a review and
synthesis. New Phytologist, Vol. 161: 371-385.
O’Leary, M.H. 1981. Review: Carbon Isotope Fractionation in Plants.
Phytochemistry, Vol. 20, No. 4, pp. 5- 567.