Root Development of Rush Skeletonweed

Abstract

In 1965–66, we observed root development of two plant types of rush skeletonweed (Chondrilla juncea L.). Rosette bud formation on both plant types occurred on the upper 5-cm zone of the taproot after seed dispersal in the fall until flower-stem initiation the following spring. Incubation at various temperatures of lateral root sections from field grown plants showed a cyclic sprouting pattern with the highest percentage during late fall and early spring, and no sprouting during June. Bud production was most frequent at the proximal end of the sections. The earlier-flowering plant type contained an average of 6.7 and 6.0 major roots after 6 and 18 months of growth whereas the late-flowering type contained 10.7 and 16.0 major roots for the same periods of growth. The early-flowering plant roots were larger in diameter than those of the late-flowering plants. Both root types increased in diameter as distance from the point of attachment increased excluding root apex. Unattached secondary plants resulting from vegetative propagation were found of both plant types.