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

Abstract

The 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.

The responses of plants to non‐uniform supplies of nutrients

“…But it changed markedly at 210//molm-=s-^ ). The root:shoot ratio of the same species was also unresponsive to P in the experiments of Stryker, Gilliam &Jackson (1974) andde Jager (1982).…”

“…First, species and treatments were selected from the Appendix for which measurements of all the variates were available. These were the experiments on Glycine max (Borkert & Barber, 1983), Hordeum vulgare (Drew, 1975;Drew & Saker, 1975, 1978, Lactuca sativa (Burns, 1991), Oryza sativa (Gile & Carrero, 1917), Plantago lanceolata, P. major and P. media (de Jager & Posno, 1979) and Zea mays (Gile & Carrero, 1917;McClure, 1972;Stryker et al, 1974;Anghmoni & Barber, 1980;de Jager 1982de Jager , 1984. Data for the responses of some species to different nutrients were treated separately.…”

Phosphorus Influx and Growth Characteristics of Corn Roots as Influenced by Phosphorus Supply1

“…Increased root growth occurred where P was present in solution at the expense of root growth in the minus P solution. The redistribution was greater the smaller the proportion of roots supplied with P. Stimulation of root growth by P has been observed in nutrient solution studies of Stryker et al (1974) with corn and Gile and Carrero (1917) with rice (Oryza sativa L.). Reducing P supply to the root resulted in a smaller ..... root radius.…”

Soybean shoot and root response to localized water and potassium in a split-pot study

“…Further, because of low vertical mobility in most soils, broadcast applications of P and K remain near the soil surface. The resulting localized P enrichment can also enhance root proliferation (Anghinoni and Barber 1980;Barber 1995;Drew 1975;Stryker et al 1974) and K uptake efficiency (Bordoli and Mallarino 1998;Borges and Mallarino 2000;Hairston et al 1990). …”