SummaryCell sap enzymes were more susceptible to heat destruction(37°) than polyribosomes whereas the latter appear relatively stable for periods up to 32 min. However, preincubating the two components together led to a more rapid disappearance of incorporating activity than did heating the components separately. Dialysis for 22 hr decreased cell sap enzyme activity 50% compared to fresh cell sap. Gel-filtrated cell sap lost a similar amount of activity when stored (3°) for 22 hr. Cell sap loses 20–25% of its activity within 24 hr during cold storage (—70°). However, polyribosomes are less susceptible losing approximately 10% of their activity. Freezing PMS (—70°) and isolating cell sap and polyribosomes 24 hr later led to a reduction in activity of 45 and 8%, respectively. PCMB lowered amino acid incorporation in the reaction media at concentrations above that of free sulfhydryl supplements.