Loss of Phosphorus-32 by Plant Roots after Foliar Application.

Abstract

Root loss of P32 to a graded series of stable P solutions and to water was studied over a long (7-day) and short (50-minute) time interval. Intact bean plants were used in which the isotope was introduced through the foliar tissue. In the long term experiment, loss to the P solutions occurred as an exponential function of ambient P concentration. P32 was also lost to the water treatment, but was conditioned by an initial effect on foliar uptake. In the short term experiment, loss to the graded P solutions also occurred as an exponent of ambient stable P. Loss to demineralized water was considerably greater than that to tap water. Loss to all treatments was greatest in the 1st 5-minute period of the study, and decreased exponentially with time. Solution treatments did not affect the basic nature of the time-course loss, but did influence the level at which it occurred.