A study of intraspecific root grafting in white pine was made. A technique for detecting root grafts by a tracer method is described. The major findings of the study were: (a) Root grafting occurs in white pine stands from 15 to 71 years of age, and probably in both younger and older stands. (b) Grafting occurs under a wide range of site conditions from bogs to dry sites. (c) Fusion may be limited to a single graft between trees, but often sizable clusters of trees are organically united by an extensive complex of self-grafts and intraspecific grafts. (d) The degree of grafting in any stand is probably related to the age, density, and purity of the stand. Also, certain certain ecotypes may be more prone than others to the establishment of grafts. (e) Roots of seemingly dead trees often remain alive through grafts to living trees. This kind of multigenotypic entity is apparently common in many pine communities. (f) Many grafts are functional in the translocation of food, minerals, and water. Translocation of food was evidence by the maintenance of growth in old living stumps. The translocation of water and minerals was demonstrated by the movement of dye and radioisotopes from tree to tree, from freshly cut sumps to trees, and from old living stumps to trees. Also, preliminary tests indicate that as F-32 injected into a root moves toward a tree, some of it may be diverted to another tree through a root graft. (g) Some grafts may not function in translocation. This was shown by the failure of dye to move from cut stumps to adjacent trees know to be grafted to the stump. Possible explanations for this behavior are that movement through some graft may occur only in one direction, that some drafts may function only in time of stress, or that some grafts may be truly nonfunctional.
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Bormann et al. (1959) studied this question.