Water Potential of Aqueous Polyethylene Glycol

Abstract

Water potential ('P) values were determined for aqueous coiloids of four molecular sizes of polyethylene glycol (PEG) using freezing-point depression and vapor-pressure deficit methods. A significant third-order interaction exists between the method used to determine 4,., PEG molecular PEG [an inert, nonionic, long-chain polymer: HOCH2-(CH2-0-CH2), CH20H (3)] has been widely used to maintain experimental media at predetermined 4.2 values (2, 7, 11, 14-16).Several researchers have reported that PEG has toxic effects on plants (5, 10). Lagerwerff et al. (8) attributed PEG 6,000 toxicity to associated heavy metals and recommended dialysis or passage through ion exchange columns to remove these impurities. Lawlor (9) suggested that PEG 1,000, 4,000, and 20,000 caused plant desiccation by blocking pathways of H20 movement.In addition to possible toxic effects, debate exists concerning the appropriate method to use for determining 'a of PEG media (8). Applegate (1) noted that the freezing-point depression of PEG 4000-Hoagland solutions of different concentrations deviated from the expected value predicted by van MATERIALS AND METHODS A laboratory advanced osmometer, model 3L (Advanced Instruments Inc., Needham Heights, MA) was used to determine the freezing-point depression of media. Vapor-pressure deficit measurements were obtained for the same media with a dew-point microvoltmeter, model HR-33, and thermocouple chamber, model C-5 1 (Wescor Inc., Logan, UT). All dew-point measurements were done at 23C. Both instruments were calibrated using the same standards. Readings in mosmol and ,uv were converted to corresponding '1. values for statistical analysis. Polythylene glycol was purchased from J. T. Baker Chemical, Phillipsburg NJ.

Glomus intraradices causes differential changes in amino acid and starch concentrations of in vitro strawberry subjected to water stress

“…However, we measured values of k0n06 MPa (SD 0n02), which is considered an inherent error of the instrument. It is interesting to note that PEG does not behave in accordance with van' t Hoff' s law (Steuter et al, 1981). The water potential for a given PEG solution is related to molarity but not linearly, varying with the molecular size of the PEG.…”

“…The water potential for a given PEG solution is related to molarity but not linearly, varying with the molecular size of the PEG. Thus, Steuter et al (1981) suggested that water potential in PEG might be controlled primarily by the matrix forces of the ethylene oxide subunits of the polymer. The measures of PEG Ψ π already presented are given only as a reference and probably underestimate the real matrix forces of such solutions.…”

Mobilização de água e conservação da viabilidade de embriões de sementes recalcitrantes de ingá (Inga vera Willd. subsp. affinis (DC.) T. D. Pennington)

“…A imersão em soluções osmóticas com potencial hídrico conhecido permite, ainda, estimar o potencial hídrico de sementes e embriões (Pammenter et al 2002, Sun 2002. Uma das soluções mais utilizadas para este tipo de tratamento é o polietileno glicol (PEG), que é um polímero de alto peso molecular, não iônico, inerte (Steuter et al 1981) e que não apresenta sinais de toxicidade para as sementes.…”

Flow Properties of Microbubble/Polyethylene Glycol Mixtures Passing through Orifices and Slits

“…This difference is attributed to the elastic property found in PEG in previous numerical and experimental researches. [18][19][20][21][22] Steuter et al 25) , Torchilinl et al 26) , and Mao et al 27) reported the elasticity of PEG was caused by the entanglement of polymer chains. Jin et al 28) , Terasaka et al 29) , and Yamada et al 30) discovered that microbubbles existed in the solutions at steady state, and that the microbubble diameter did not change.…”