18O enrichment in phosphorus pools extracted from soybean leaves.

The New phytologist (2012-10-31)
Verena Pfahler, Thilo Dürr-Auster, Federica Tamburini, M Stefano Bernasconi, Emmanuel Frossard
ABSTRACT

The objective of this study was to investigate the isotopic composition of oxygen bound to phosphate (δ(18)O-PO(4)) in different phosphorus (P) pools in plant leaves. As a model plant we used soybean (Glycine max cv Toliman) grown in the presence of ample P in hydroponic cultures. The leaf blades were extracted with 0.3 M trichloroacetic acid (TCA) and with 10 M nitric acid. These extractions allowed measurement of the TCA-soluble reactive P (TCA P) that is rapidly cycled within the cell and the total leaf P. The difference between total leaf P and TCA P yielded the structural P which includes organic P compounds not extractable by TCA. P uptake and its translocation and transformation within the soybean plants lead to an (18)O enrichment of TCA P (δ(18)O-PO(4) between 16.9 and 27.5‰) and structural P (δ(18)O-PO(4) between 42.6 and 68.0 ‰) compared with 12.4‰ in the phosphate in the nutrient solution. δ(18)O values of phosphate extracted from soybean leaves grown under optimal conditions are greater than the δ(18)O-PO(4) values of the provided P source. Furthermore, the δ(18)O-PO(4) of TCA P seems to be controlled by the δ(18)O of leaf water and the activity of inorganic pyrophosphatase or other pyrophosphatases.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Trichloroacetic acid, ACS reagent, ≥99.0%
Sigma-Aldrich
Trichloroacetic acid solution, 6.1 N
Sigma-Aldrich
Trichloroacetic acid, BioXtra, ≥99.0%
Sigma-Aldrich
Trichloroacetic acid, ≥99.0% (titration)
Sigma-Aldrich
Pyrophosphatase, Inorganic from baker's yeast (S. cerevisiae), powder, ≥500 units/mg protein (E1%/280)
Sigma-Aldrich
Trichloroacetic acid, BioUltra, ≥99.5% (T)
Sigma-Aldrich
Trichloroacetic acid, suitable for electrophoresis, suitable for fixing solution (for IEF and PAGE gels), ≥99%
Sigma-Aldrich
Trichloroacetic acid, ACS reagent, for the determination of Fe in blood according to Heilmeyer, ≥99.5%
Sigma-Aldrich
Pyrophosphatase, Inorganic from Escherichia coli, recombinant, expressed in E. coli, lyophilized powder, ≥90%, ≥800 units/mg protein