SOME LOW-TEMPERATURE EFFECTS ON SIEVE TUBE TRANSLOCATION IN SALIX-VIMINALIS

The data presented on translocation of 14C-labelled compounds in Salix viminalis show that above a temperature close to -4 °C translocation occurs, whilst below -4 °C in most cases it does not.Stoppages were irreversible when the temperature of the cooled stem was raised again to normal (approximately 20 °C) and appeared to involve some disruption of the phloem. The temperatures at which the bark was found to freeze were found to be closely similar, with respect to level and variability, to the stopping temperature.Respiration measurements on isolated strips of bark at -2 °C showed that oxygen uptake fell to approximately 5 per cent of its value at 25 °C.The decreased level of radioactivity in the cooled regions of the stems is considered to be evidence that the exchange of labelled compounds between the sieve tubes and the surrounding cells was slowed up at low temperatures. © 1969 OXFORD UNIVERSITY PRESS.