3Vickey H B, Puclier R. The assimilation study with isotopic nitrogen [ J ]. Bicl chem. 1940,135 : 531.
4Yoshida D. The translocation of labeled nitrogen absorbed from root and injected into leaves of tobacco plant with special reference to alkaloid synthesis[ J ]. Soil Sci. Plant Nutr. Tokyo. 1962, (8) : 39-40.
5Volk R, Mcauliffe C. Factors affecting the foliar absorption of ^15N labeled urea by tobacco soil[ J]. Sci Soc. Am. Proc. 1954,18:308.
