Carbon Fractionation within Individual Plants MEAS 760 Lori Skidmore & Jonathon Harris

C 13 within Plants Does C 13 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 –Farquhar et al –Hobbie and Werner 2004 Prairie Ridge Data Summary

Does C 13 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  13C of different plant parts (leaves, roots) are common. Since most  13C 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 Roots are slightly depleted in heavier isotope, compared to shoots but not when compared to leaves. Table 3 Werth & Kuzyakov 2006

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 amino- acids 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 HCO 3 - becomes enriched in  C13 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 Reactions and transport processes affect composition of compounds in different plant tissues. Movement and isotopic fractionation of carbon between leaves and roots results in 13C- depleted 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 Sample IDLeafFlowerStemRoot C3 Ambrosia artemisiifolia (Ragweed) PRP PRP C3 Solanaceae carolinense PRP (Horsenettle) GRASSES Plant typePlant name Sample IDGreen bladeBrown bladeStemRoot C3 Festuca (Fescue) PRP PRP C4 Cynodon dactyla (Bermuda grass) PRP PRP PRP PRP

Results: Broadleaf plants Average  13C (% o ) [*Part*  13C – Leaf  13C] Ragweed –Leaf = –Flower = [ ] –Stem = [ ] –Root = [ ] Horsenettle –Leaf = –Stem = [+1.92] –Root = [ +2.79] Ragweed Horsenettle

Results: Grasses Average  13C (% o ) [*Part*  13C – Green blade  13C] Bermuda grass –Green blade = –Brown blade = [ ] –Stem = [-0.047] –Root = [+0.733] Fescue –Green blade = –Brown blade = [+0.085] –Root = [+3.545] Bermuda grass Fescue

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  13C 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 ( % o ) and leaves ( % 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 Abelson, P.H. and T.C. Hoering Carbon isotope fractionation in formation of aminoacids by photosynthetic organisms. Biogeochemistry, 47: Chikaraishi Y, Naraoka H 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 Compound specific  13C analyses of leaf lipids from plants with differing carbon dioxide metabolisms. Organic Geochemistry 21: 619–627. Hillaire-Marcel, G 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 Hobbie, E.A. and R.A. Werner Intramolecular, compound-specific, and bulk carbon isotope patterns in C3 and C4 plants: a review and synthesis. New Phytologist, Vol. 161: O’Leary, M.H Review: Carbon Isotope Fractionation in Plants. Phytochemistry, Vol. 20, No. 4, pp