Permeability Changes in Senescing Tissue

Measurements of K + leakage and apparent free space (A.F.S.) to 14C glycerol and 14C sucrose indicated permeability changes in senescing Phaseolus multiflorus cotyledons, and Arum maculatum spadix. A.F.S. to glycerol was found to in crease in two steps, the first of which took place early in development. A com parative study of respiration showed that permeability changes occur before any changes in the rate of respiration. They are an early sign of senescence. The similarity of the increasing changes in leakage of K+, A.F.S. to glycerol and sucrose, and permeability across the membrane surrounding the osmotic volume in the two different materials suggests that they are of general occurrence.