The Translocation of 3,5-Dichlorophenoxyacetic Acid in Relation to its Effect on Potato Common Scab

Abstract

The translocation of 3,5-dichlorophenoxyacetic acid (3,5-D) in the potato plant was studied to clarify the mode of action against potato common scab. 3,5-D was translocated to the tuber faster and metabolised less than 2,4-D. Translocation to tubers was proportional to growth and a concentration of 10-25 nmol 3,5-D g_1 fr. wt. was attained 8 d after a foliar application. Previous evidence indicates this concentration was insufficient to be directly toxic to the pathogen Streptomyces scabies and the results suggest that 3,5-D acts in the tuber by altering the host's response to infection.