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This article in AJ

  1. Vol. 66 No. 4, p. 554-557

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Phosphate Uptake Rate of Corn Roots as Related to the Proportion of the Roots Exposed to Phosphate1

  1. A. Jungk and
  2. S. A. Barber2



Little information is available on the effect of reducing the proportion of a plants roots in contact with P on the rate of P uptake by those roots. Three experiments were conducted with corn (Zea mays L.) in solution culture in a growth chamber. In the first experiment trimming roots to reduce root length per plant gave results on P uptake similar to using a split-root system where a portion of the roots were in a nutrient solution containing 50 μM P. Uptake of P over an 8-hour or shorter period was in proportion to the length of root exposed to the P solution. Hence, phosphorus uptake rate per unit of root was not increased by reducing the proportion of the root in contact with P. In an experiment conducted over a 4-day period, with P levels of 100 and 1000 μM, an increase of 20 to 40% P uptake per unit of root occurred when root length was reduced to 37 to 58% by trimming. A lower P level in the plants with trimmed roots as compared to those with untrimmed roots may have caused the increase in P uptake rate per meter of root. In a 4-hour experiment with P concentrations between 5 and 10 μM, trimming the roots did not increase the P uptake rate per unit of root length. The results indicate that it is necessary to supply P to a large proportion of the roots in order to adequately supply the plant.

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