Indirect Compartmental Analysis of Copper in Live Ryegrass Roots; Comparison with Model Systems

The technique of indirect compartmental analysis of 64Cu elution measurements was applied to cellulose discs, a ryegrass (Lolium perenne L. cv. Premo) root cell wall isolate and live and dead roots of whole ryegrass seedlings. Curves of logarithm counts remaining in the material versus time resolved into four phases in each case. The half-time of exchange of the slowest compartment ranged from 3.6 to 66.1 h for cellulose discs and live ryegrass roots, respectively. Plots of logarithm efflux versus time again resolved into four phases for cellulose discs, isolated root cell wall, and dead ryegrass roots; the efflux of these materials obeyed first order kinetics. In live ryegrass roots the plot of logarithm efflux versus time could not be resolved beyond the initial curve; efflux from live ryegrass roots did not obey first order kinetics. A full compartmental analysis of copper in live ryegrass roots could not be performed. It is suggested that, in live ryegrass roots, cell wall adsorption sites are responsible for a wide continuous range of half-time of exchange values which overlie the elution curves of the vacuolar and cytoplasmic compartments. The technique of indirect compartmental analysis artificially splits the total elution curve into four discrete compartments, the slowest of which has contributions from both the vacuole and cell wall.