A dual isotopic approach using radioactive phosphorus and the isotopic composition of oxygen associated to phosphorus to understand plant reaction to a change in P nutrition

BACKGROUND: Changing the phosphorus (P) nutrition leads to changes in plant metabolism. The aim of this study was to investigate how these changes are reflected in the distribution of (33)P and the isotopic composition of oxygen associated to P (δ(18)O(P)) in different plant parts of soybean (Glycine max cv. Toliman). Two P pools were extracted sequentially with 0.3 M trichloroacetic acid (TCA P) and 10 M nitric acid (HNO(3); residual P). RESULTS: The δ(18)O(P) of TCA P in the old leaves of the − P plants (23.8‰) significantly decreased compared to the + P plants (27.4‰). The (33)P data point to an enhanced mobilisation of P from residual P in the old leaves of the − P plants compared to the + P plants. CONCLUSIONS: Omitting P for 10 days lead to a translocation of P from source to sink organs in soybeans. This was accompanied by a significant lowering of the δ(18)O(P) of TCA P in the source organs due to the enzymatic hydrolysis of organic P. Combining (33)P and δ(18)O(P) can provide useful insights in plant responses to P omission at an early stage.