Artificially Induced Water and Sulfate Transport through Sunflower Roots

Abstract

AbstractA new experimental method is used to determine simultaneously the quantity and composition of the sap exuded by a detopped root system at the same time that a pressure deficit of desired magnitude can be applied to the stem stump.The technique was used in a study of the transport of radioactive sulfate through the roots of young sunflower plants placed on complete nutrient solutions labelled with 35S.The complications by the time factor on the composition and rate of the sap stream in experiments of this type were observed and discussed. The time of detopping the roots was very critical as the conditions of sulfate transport were greatly changed some time after the excision.A rectilinear connection existed between the rate of sulfate transport in the sap and the water flow at sap flow velocities comparable with transpiration rates. When the transport of water was very slow, the rate of sulfate transport became constant and independent of the water stream. It was suggested that diffusion or water flow could act as motive force for the ion transport in some non‐metabolic phase of transfer in the roots. The addition of 2,4‐DNP to the test solution severely interfered with the water and sulfate transport conditions in the roots.