Anatomical modification by 2,4-DB of vascular cambium and secondary xylem in soybean internodes

Anatomical changes in the vascular cambium and secondary xylem of the first internode of soybeans were observed 15 days after an aqueous spray of 4-(2,4-dichlorophenoxy)butyric acid (2,4-DB) was applied at 0.56 kg acid equivalent per hectare. The cambium became a meristem of initials, which were intermediate in morphology between normal ray and fusiform initials, and the system of ray initials was lost. The xylem lost its rays and became a tissue in which narrow vessel members abnormally outnumbered the axial parenchyma cells, libriform fibers, and gelatinous fibers which were common in normal wood. The herbicide inhibited the normal expansion of vessel-member primordia.