Advisor

Todd N. Rosenstiel

Date of Award

1-1-2010

Document Type

Thesis

Degree Name

Master of Science (M.S.) in Biology

Department

Biology

Physical Description

1 online resource (v, 82 p.) : ill. (some col.)

Subjects

Root Carbon Fixation, Root Respiration, PEP Carboxylase, Poplar, Rhizodeposition, Roots (Botany) -- Research, Plants -- Effect of atmospheric carbon dioxide on, Carbon dioxide -- Metabolism, Plants -- Respiration

DOI

10.15760/etd.345

Abstract

Roots live in and have evolved in a high carbon dioxide (CO₂) environment, yet relatively little research has been conducted on the impacts of soil dissolved inorganic carbon (DIC) on root metabolism. In this thesis, I explore the impacts of root-zone DIC on whole plant biomass accumulation, water use efficiency, and above-ground gas exchange. In addition, I explore the impacts of root-zone DIC on root processes: root PEP-Carboxylase activity, root respiration rate and root exudation of Krebs cycle organic acids. Root-zone DIC did not impact biomass accumulation, leaf gas exchange parameters or water use efficiency under the growth conditions examined. Root-zone DIC did increase root PEP-Carboxylase activity, but decreased root respiration (both CO₂ production and O₂ consumption) and decreased organic acid exudation rates. Increase in measurement CO₂ partial pressure was found to cause an instantaneous decrease in root CO₂ production, and I provide evidence that changes in root metabolism (CO₂ uptake by roots) are part of the cause of this phenomenon. A hypothesized relationship between root respiration rate and Krebs cycle organic acid exudation was not supported by my data. I conclude that root-zone DIC has important impacts on critical functions of root metabolism, and should be considered as an important abiotic factor much in the same way atmospheric CO₂ is for leaves and whole plant biology.

Description

Portland State University. Dept. of Biology

Persistent Identifier

http://archives.pdx.edu/ds/psu/7061

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