The effects of coumarin on the translocation of 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) in bean (Phaseolus vulgarisL. cv. Stringless Greenpod) seedlings was determined.14C-labeled 2,4,5-T was injected in the stem tissue at the cotyledonary node along with the coumarin or the coumarin was added to the nutrient solution prior to, or at the time of, 2,4,5-T treatment. The amount of translocation of radioactive 2,4,5-T to plant parts was then determined at various times after treatment. An immediate effect of coumarin was to enhance acropetal 2,4,5-T translocation to the young shoots. This effect occurred at low 2,4,5-T treatment levels and appeared to be specific for 2,4,5-T since sucrose translocation was not affected. Prolonged treatment with coumarin inhibited acropetal and basipetal 2,4,5-T translocation in a manner similar to prolonged treatment with abscisic acid (ABA). Gibberellin A3(GA) reversed the inhibitory effects of coumarin and ABA on 2,4,5-T acropetal translocation.
展开▼
