Studies on ribosomes from barley leaves. Changes during senescence.

The effect of sucrose, Mg(2+) and deoxycholate on the yield of ribosomes from barley leaves was determined and the changes in the amount and the composition of ribosomes during senescence of intact and excised first seedling leaves were examined.The extraction medium containing 20 mm tris-HCl, 0.25 m sucrose, 1 mm MgCl(2) and 0.5% deoxycholate (pH 7.8) gave the maximum yield of polyribosomes and ribosomes. That polyribosomes were not non-specific aggregates was suggested by their capacity to synthesize nascent protein. During senescence of both intact and excised leaves polyribosomes and ribosomes were lost and the ribosomes-polyribosomes which originally contained 48% protein and 52% RNA showed substantial decline in the protein content during senescence indicating the degradation of ribosomes and the loss of their function.