Translocation of Assimilates and Dalapon in Established Johnsongrass

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Abstract
The influence of repeated clipping of the shoots on the translocation of 14C-assimilates and 2,2-dichloropropionic acid 2-14C (dalapon) into the rhizome system of established johnsongrass (Sorghum halepense (L.) Pers.) was studied when regrowth was in the preboot, boot, and flowering stages. Radioautography and radio-assay procedures were used to follow the distribution of label within the plants. Plants defoliated three times prior to treatment showed no increase in basipetal translocation over plants defoliated once. As plants matured to the flowering stage, assimilate translocation into rhizomes increased. This increase was closely related to the degree of secondary rhizome growth occurring at time of label application. During preboot, assimilate movement was restricted to rhizome apices with very little retention in intervening tissue. Labeled dalapon followed a similar translocation pattern to that of assimilates. The role of assimilate translocation and storage as correlated with life cycle changes in carbohydrate nutrition of established johnsongrass is discussed.