RADIOISOTOPES

During 1981–2000, my research focused on the precise determination of the natural abundances of the ¹³C/¹²C and ¹⁵N/¹⁴N ratios (δ¹³C, δ¹⁵N) in many samples of plant tissues and metabolites. That research benefited from the previous work performed by pioneers in this field. My studies during that period provided the followings; (1) the identification of significant differences in the δ¹³C values in plant tissues and phloem sap affected by biotic (N acquisition, plant species and cultivars) and abiotic (drought) factors, (2) the discrimination of ¹⁵N/¹⁴N during the uptake, metabolism, and translocation of nitrate, ammonium and biologically-fixed N, and (3) the application of δ¹³C and δ¹⁵N tracing techniques for the quantification of plant residue dynamics (i.e., accumulation and degradation) in soils, plant N uptake from different sources (soils, chemical fertilizers, organic manures) and field biological N₂ fixation by legumes including trees and non-legumes such as sugarcane and sweet potato, respectively. Here I review my publications and findings which gave insight for a precise understanding of whole plant C/N metabolisms.