Nonuniform Phosphorus Distribution in the Root Zone of Corn: Growth and Phosphorus Uptake

Abstract

AbstractThe implications of nonuniform P distributions in the root zone of corn (Zea mays L.) on growth and P uptake were explored utilizing a split root system. Maximal dry matter accumulation occurred only when the entire root system was exposed to an external P supply. Reduction in shoot growth of nearly 20% was associated with those P distributions in which part of the root system was devoid of an external P supply. There was a concomitant decrease in root growth in “no P” zones such that shoot/root ratios remained constant regardless of whether all or part of the root system was exposed to P. The growth rate of roots dependent on an internal supply of P via translocation (roots in “no P” zones), as contrasted to that of roots with an external supply, is considered to have been limited by the rate at which inorganic P was supplied to the growing points.These effects were not due to the lack of total P uptake for it was shown that a portion of the root system could take up high amounts of P if the external supply was sufficient.For P distributions with one root zone devoid of an external P supply, significant differences in P concentrations, leaf widths, and dry weight occurred between opposite sides of some leaves. It is postulated that these nonuniform effects on leaves were the result of nonuniform P transport from the roots to leaves.