The Exudation from Excised Maize Roots Bathed in Sulphate Media

The fluid exudation fluxes of excised maize roots bathed ina variety of K₂SO₄ solutions have been measured, along withthe ionic concentrations and osmolalities of the exudates. Anapparent imbalance of inorganic ionic charge in the exudate,and a discrepancy in the total salt concentrations comparedwith the measured osmolalities, suggest the presence of significantamounts of organic anions in the exuded fluid. Thin-layer chromatographicmethods indicate these to be mainly amino-acids and organicacids of the Kreb's cycle. Linear regression analysis showsthat the exudation flux is satisfactorily described by a simpleosmotic process together with a constant non-osmotic water fluxof 0.43 µ1 cm^-2 h^-1. The osmotic permeability for theroot is found to be 0.18 x 10^-6 cm sec^-1 atm^-1. The exudationfrom sulphate media is contrasted with that from chloride media.