Translocation coefficients, computed for unit ground area, are require
d in crop models as part of the simulation of the partitioning of assi
milates. An equation for translocation is derived by considering press
ure-driven flow and the physical dimensions of the pathway in the phlo
em. Numerical estimates of the translocation coefficients for grasses
and trees are calculated using anatomical data. The values found are c
ompatible with published rates of translocation in the phloem. (C) Ann
als of Botany Company