The effect of water stress on the translocation of recent photosynthate to the roots of young plants of Pinus strobus

White pine plants in their third year of growth were maintained for a 4-month period on soil having a moisture content of either 7% or 14%. In September, at the end of this period and at a time when translocation to the root is known to be high, the plants were permitted to photoassimilate 14CO2, and 8 hours later the distribution of 14C among the root, the old shoot, and the new shoot was determined.The plants maintained for the 4-month period on the 7% soil moisture environment had values for new needle length and root and new shoot fresh weights which were approximately 55–60% of the values from those plants grown on the higher soil moisture environment. However, despite such retarded growth, the magnitude of translocation to the root during the 8 hours after 14CO2 assimilation was only slightly lower in those plants grown on the lower soil moisture environment.From the results it is suggested that the decreased amount of translocation to the roots previously observed in pine plants in June and July cannot be attributed to reduced root metabolic activity and growth caused at that time by lowered soil water content.