Nitrogen Influence on Phosphorus Uptake by Pinus Radiata Seedlings

Nitrogen pretreatment of 8-week-old Pinus radiata seedlings low in phosphorus increased P absorption and translocation during a 6-hr uptake period. This stimulation occurred in both mycorrhizal and nonmycorrhizal seedlings. Nitrate and ammonium forms of N were both effective in increasing P uptake except that at the highest level (100 ppm N) NH4N caused a decrease in nonmycorrhizal seedlings. Adequate P was absorbed by seedlings from solutions containing from 0.75 ppm to 0.007 ppm P. Increases of P concentration in the solution stimulated both N and P uptake. The P accumulation in the roots of seedlings high in P at the time of pretreatment was not stimulated due to N pretreatment, but P translocation to the tops did increase. Forest Sci. 18:126-132.