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Oxygen Availability in Polyethylene Glycol Solutions and Its Implications in Plant-Water Relations ¹

^a Department of Forest and Wood Sciences and Departments of Civil Engineering and Microbiology, Colorado State University, Fort Collins, Colorado 80523

The solubility of O₂ in polyethylene glycol 4000 and 6000 solutions of varying concentrations was determined iodimetrically (titrimetrically) and electrochemically using a rotating glassy carbon electrode and a PAR Model 174 Polarograph. The titrimetric determination resulted in the formation of an unexpected precipitate at 2% (w/v) polyethylene glycol corresponding to the approximate critical micelle concentration of the two polyethylene glycol homologs. Beyond 5% polyethylene glycol, O₂ concentration was inversely proportional to polyethylene glycol concentration, and was higher in polyethylene glycol 4000 solutions than in polyethylene glycol 6000. The electrochemical data are a direct measure of O₂ transport to the electrode surface, rather than O₂ activity or concentration. Results indicate that even at relatively high H₂O potentials, the transport of O₂ to the root surface might be insufficient to meet the plant's respiratory requirements.

³ Departments of Civil Engineering and Microbiology.

¹ This research was supported by National Science Foundation Grant GB-19928 and by a grant from the Pacific Northwest Forest and Range Experiment Station, Forest Service, United States Department of Agriculture.

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