Quantitative imaging of 33P in plant materials using 14C polymer references

Phosphorus (P) research still lacks techniques for rapid imaging of P use and allocation in different soil, sediment, and biological systems in a quantitative manner. In this study, we describe a time-saving and cost-efficient digital autoradiographic method for in situ quantitative imaging of P-33 radioisotopes in plant materials. Our method combines autoradiography of the radiotracer applications with additions of commercially available C-14 polymer references to obtain P-33 activities in a quantitative manner up to 2000Bqcm(-2). Our data show that linear standard regressions for both radioisotopes are obtained, allowing the establishment of photostimulated luminescence equivalence between both radioisotopes with a factor of 9.73. Validating experiments revealed a good agreement between the calculated and applied P-33 activity (R-2=0.96). This finding was also valid for the co-exposure of C-14 polymer references and P-33 radioisotope specific activities in excised plant leaves for both maize (R-2=0.99) and wheat (R-2=0.99). The outlined autoradiographic quantification procedure retrieved 100%+/- 12% of the P-33 activity in the plant leaves, irrespective of plant tissue density. The simplicity of this methodology opens up new perspectives for fast quantitative imaging of P-33 in biological systems and likely, thus, also for other environmental compartments.