Nitrogen Flux into Corn Roots as Influenced by Shoot Requirement
1976
Edwards, J. H. | Barber, S. A.
Knowledge of the N flux characteristics of corn (Zea mays L.) roots is important in determining the N fertilizer practices needed for efficient N fertilizer use. Fertilizing a portion of the root system with N increases the N uptake required per unit of root fertilized over that in which all roots are fertilized with N. The effect that fertilizing a portion of the roots with N has on the N influx characteristics of corn roots has not been evaluated. Hence the objective of this research was to determine if shoot N requirement influenced N influx/m of corn root. Trimmed- and split-root procedures were used in solution culture experiments in the growth chamber to vary the amount of N-absorbing roots/unit of shoot and determine its effect on N influx. Both NH⁺₄ and NO⁻₃ forms of N were used. Trimming corn roots 2 days before measuring influx resulted in only small increases in N influx/m of root so that N uptake/plant was greatly reduced by trimming. Splitting the roots between N-containing and N-free solutions from seedling stage until 16 or 18 days, when influx was measured, resulted in larger increases in net N influx than when the roots were trimmed 2 days before influx measurement. Nitrogen level within the root was not related to N uptake rate/m of root in either experiment. It appears that increasing shoot demand for N does not immediately affect N influx into the root but that the capability for higher N influx is developed when plants are grown under N stress.
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