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| Titel |
Leaf physiological processes strongly affect δH2 values of leaf wax n-alkanes in C3 and C4 grasses. |
| VerfasserIn |
Bruno Gamarra, Dirk Sachse, Ansgar Kahmen |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250081717
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| Zusammenfassung |
| Leaf wax n-alkanes are naturally synthesized saturated hydrocarbons. They are
synthesized as part of plant leaf cuticle as a mechanism to prevent water losses.
Two of the most important features of n-alkanes are their enormous environmental
persistence and terrestrial ubiquity making them a solid and reliable long-term
and large-scale biomarker. Their hydrogen isotopic composition (δH2) of leaf wax
n-alkanes has been traditionally related to precipitation. Leaf wax n-alkanes and their
δH2 values have thus been celebrated as biomarkers to reconstruct hydrological
changes.
δH2 values of leaf wax n-alkanes are yet to be fully comprehended. They are basically
determined by three mechanisms: (1) The δH2 value of the plant source water (2) leaf water
evaporative enrichment in H2 and (3) biosynthetic fractionation and depletion in H2during
their biosynthesis from leaf water. Out of these three, the exact degree by which the
evaporative H2-enrichment of leaf water influences the δH2 values of leaf wax n-alkanes is
still unknown.
We conducted an experiment where we tested and quantified the effects of leaf water
evaporative H2-enrichment on the leaf wax n-alkane δH2 values of different grass species.
We grew 12 C3 and C4 grass species under controlled environmental conditions in growth
chambers. The plants were exposed to 3 different levels of air relative humidity (45, 65 and
85%). These treatments were to generate different degrees of leaf water H2-enrichment in the
plants. The goal of our experiment was to determine by what degree the different levels
of leaf water H2-enrichment influence the δH2 values of the different C3 and C4
grass species. Additional measurements of gas exchange, evapotranspiration and
leaf length and area accompanied the isotopic analysis in order to explain species
variability.
Our experiments showed that leaf water evaporative H2-enrichment has a critical impact
on leaf wax n-alkane δH2 values of all studied plants. The magnitude was species specific,
e.g. for D. glomerata the influence of leaf water evaporative Deuterium-enrichment on leaf
wax n-alkanes δH2 values was about 100%; but for other species the influence ranged from
25 to 90%. In our presentation we will relate these different contributions of leaf water δH2
values to differences in species’ morphology and/or physiology.
Key words: plant physiology, stable hydrogen isotopes, evaporative H2-enrichment, leaf
wax n-alkanes, paleoclimate |
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