Absorption and translocation of 2, 4-dichlorophenoxyacetic acid and of radioactive phosphorus

Plant responses to sublethal concentrations of 2,4-D

“…There is evidence that 2,4-D is more readily absorbed as an undissociated molecule (4,52). Investigators (4,12,52).…”

“…There is evidence that 2,4-D is more readily absorbed as an undissociated molecule (4,52). Investigators (4,12,52). also report that Q 10 data indicate the absorption process is not simple diffusion but rather some type of chemical or enzymatic reaction.…”

“…Leopold (47) reports movement may occur: 1) in the xylem along with the transpiration stream, 2) through the phloem or other cells such as ray parenchyma, 3) through the cell walls, or 4) through the intercellular spaces. Several investigators have reported that translocation of 2,4-D is closely associated with translocation of carbohydrates(4,5,15,21,58,66) . In multi-leaved bean plants, absorption and translocation were greatest from the lower unifoliate leaves, less from successively higher leaves and that no 2,4-D was transported from young leaves that were still importing food from more mature parts of the plants.Barrier (4) has shown that in soybeans a supply of sucrose is necessary for translocation of 2,4-D and that any 2,4-D absorbed is held in the leaves until carbohydrates become available.These workers indicate that 2,4-D moves upward through the xylem when absorbed by the roots and up and down in the plant through the phloem at a rate dependent on temperature .…”

“…In multi-leaved bean plants, absorption and translocation were greatest from the lower unifoliate leaves, less from successively higher leaves and that no 2,4-D was transported from young leaves that were still importing food from more mature parts of the plants.Barrier (4) has shown that in soybeans a supply of sucrose is necessary for translocation of 2,4-D and that any 2,4-D absorbed is held in the leaves until carbohydrates become available.These workers indicate that 2,4-D moves upward through the xylem when absorbed by the roots and up and down in the plant through the phloem at a rate dependent on temperature . The rates of translocation of 2,4-D show the temperature coefficient of a chemical reaction(4,5). This may be as fast as 9 meters per hour in the zylem and 10 to 100 centimeters per hour in the phloem(47) but showing some variability depending on the concentration in which higher levels increase absorption but decrease translocation, and also depending on the use of a surfactant which may enhance both absorption and translocation.…”