Element absorption and hydration potential of polyacrylamide gels

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Abstract
Element absorption and hydration potential (HP) of two polyacrylamide gels (Aa and Bb) were studied after incubation in Hoagland's nutrient solution concentrations of either 2X, 1X, 0.5X, 0.25X, 0.125X, or 0X (deionized water). Element absorption was observed and analyzed by making transects from the gel granule surface to center on a Phillips CM12S scanning transmission electron microscope (STEM) equipped with an EDAX 9800 plus EDS unit for x‐ray micro analysis. Thick sections were cut on dry glass knives using an RMC MT6000 ultramicrotome. Surface analysis of bulk specimens was also made with an AMR 1000A scanning electron microscope plus PGT1000 EDS unit. Overall, gel HP decreased curvilinearly as solution concentration increased linearly; however, HP was generally higher for gel Bb than for Aa. Surface analysis of both gels compounds (1X concentration) revealed the presence Ca, Zn, and K. Additionally, Mn, S, and P in trace amounts, and Fe were found at the surface of gel Aa. Furthermore, Fe and P in trace amounts, Mg, and S were found at the surface of gel Bb. STEM analysis of both gels (1X concentration) showed a general diminished presence of all elements from the gel surface to center signifying partial element migration. We conclude that gel HP is linked to element absorption and migration of a Hoagland's solution into the gel matrix, particularly Ca, Zn, and K. However, element migration into the gel matrix is not the same for all polyacrylamide gel compounds. Polyacrylamide gels might improve plant growth under saline conditions by absorbing cation salts into the gel granule.