This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via CrossRef Citing Articles via Web of Science (9) Citing Articles via Google Scholar Google Scholar Articles by Smith, F. W. Articles by Jackson, W. A. Search for Related Content PubMed PubMed Citation Articles by Smith, F. W. Articles by Jackson, W. A. Agricola Articles by Smith, F. W. Articles by Jackson, W. A.

Environmental and Stress Physiology

Nitrogen Enhancement of Phosphate Transport in Roots of Zea mays L. ¹

I. Effects of Ammonium and Nitrate Pretreatment

Division of Tropical Crops and Pastures, Commonwealth Scientific and Industrial Research Organization, Cunningham Laboratory, St. Lucia, Queensland 4067, Australia, Department of Soil Science, North Carolina State University, Raleigh, North Carolina 27695-7619

The effect of nitrogen status on phosphorous uptake and translocation was examined in 6-day-old dark-grown decapitated maize seedlings exposed to 25 micromolar phosphorous. Transfer to complete solutions containing 1 millimolar ammonium resulted in an increase in phosphorous uptake rate after 6 to 8 hours. The stimulus remained effective for at least 5.5 hours upon subsequent transfer to nitrogen-free solutions. Pretreatments for 16 hours with either nitrate or ammonium resulted in enhanced rates of subsequent phosphorous uptake and in enhanced translocation to the xylem of the exogenously supplied phosphorous. Both processes reached a plateau following pretreatment with 0.1 to 1.0 millimolar concentrations of either nitrogen ion. Further enhancement occurred with 10 millimolar nitrate, but not with 10 millimolar ammonium pretreatment. Although nitrogen pretreatments slightly increased the quantity of exogenous phosphorous retained in the root tissue, most of the extra phosphorous taken up by the nitrogen-pretreated seedlings was translocated to the xylem. The enhanced translocation, however, did not totally account for the increase in uptake implying a specific stimulation of the uptake process.