PROTON AND COPPER ADSORPTION TO MAIZE (ZEA MAYS L.) AND SOYBEAN (GLYCINE MAX (L.) MERR.) ROOT CELL WALLS

The pectic polysaccharides in the cell walls of plant roots create a negative surface charge. In this dissertation, reviews of cell wall biochemistry, isolation methods, theoretical approaches to cell wall ion exchange, and possible effects of cell wall exchange on plant physiology are presented. The literature indicates that specific adsorption, as well as electrostatic interactions, must be invoked to model cell wall ion exchange.;A preliminary model which includes apoplast exchange in simulation of nutrient uptake is reviewed. Simulations of cell wall speciation indicate that at typical soil solution concentrations, most Cu;A surface complexation model which has been used to describe inner-sphere complexation on oxide surfaces was applied successfully to the adsorption of Cu by isolated cell walls of 4-d and 28-d-old maize (Zea mays L.) and 21-d old soybean (Glycine max (L.) Merr.) roots. Values obtained for the intrinsic pK of the titratable carboxyl groups were 3.2 (4-d maize), 3.6 (28-d maize), and 3.0 (21-d soybean) as determined by potentiometric titration with either NaOH or HCl in 20 mol m...