Document: BRE-3-31-12

Why is a grass blade like a tree ring? An isotopic model for recording environmental data in grass blades.

HELLIKER, B.R* and J.REHLERINGER

University of Utah, Salt Lake City, UT 84112 USA 1

Abstract:
We present a model to explain the organic oxygen isotope signature in grass leaf blades and to show that grass blades are analogous to tree rings in recording environmental information. The growth portion of the model is based on intercalary meristem growth. Cells for grass blade growth result from cell division at the basal intercalary meristem, but receive carbohydrates for growth from distal portions of the grass blade. The isotope model is based on isotope tree ring models that incorporate the ways in which relative humidity and water source information influence organic oxygen isotope ratios. This model was applied, with slight modification, to grass leaves. The results of the model agreed well with observed oxygen isotope ratios in grass blade cellulose. Therefore, we expect that oxygen isotope ratios of cellulose along the length of a grass leaf blade provide a continuous environmental record during the period of leaf growth.

Keywords: grasses; stable isotopes; oxygen isotopes

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This abstract is being presented at: 9:15 AM in session:
Oral Session #9: Respiration and Isotopes.