Translocation at 0° C inHelianthus annuus

Potassium uptake by Helianthus annuus plants growing in water culture was found to be closely dependent upon the translocation of sugar to the roots. This relationship was used to determine the effect of cooling on the rate of translocation. A Q10 of approximately 3 over the range 0–25° C was obtained but tracer experiments showed that translocation was not stopped at 0° C. A complete recovery in translocation rate appeared to occur in some experiments after prolonged cooling. It is concluded that this can only be satisfactorily explained on the assumption that carbohydrates move in the sieve tubes by mass flow. The driving force of such a mass flow is considered to be located in each sieve element.