Quantitative imaging of 33P in plant materials using 14C polymerreferences

Phosphorus (P) research still lacks techniques for rapid imaging of P use and allocation in different soil, sediment, and biologicalsystems in a quantitative manner. In this study, we describe a time-saving and cost-efficient digital autoradiographic method for insitu quantitative imaging of 33P radioisotopes in plant materials. Our method combines autoradiography of the radiotracerapplications with additions of commercially available 14C polymer references to obtain 33P activities in a quantitative mannerup to 2000 Bq cm−2. Our data show that linear standard regressions for both radioisotopes are obtained, allowing the establishmentof photostimulated luminescence equivalence between both radioisotopes with a factor of 9.73. Validating experimentsrevealed a good agreement between the calculated and applied 33P activity (R2 = 0.96). This finding was also valid for the coexposureof 14C polymer references and 33P radioisotope specific activities in excised plant leaves for both maize (R2 = 0.99) andwheat (R2 = 0.99). The outlined autoradiographic quantification procedure retrieved 100% ± 12% of the 33P activity in the plantleaves, irrespective of plant tissue density. The simplicity of this methodology opens up new perspectives for fast quantitativeimaging of 33P in biological systems and likely, thus, also for other environmental compartments