¹⁸O enrichment in phosphorus pools extracted from soybean leaves

Abstract

O of leaf water, d18 O-PO 4 , soybean, structural P, TCA-soluble reactive P (TCA P). SummaryThe objective of this study was to investigate the isotopic composition of oxygen bound to phosphate (d 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

Oxygen isotope ratios of plant available phosphate in lowland tropical forest soils

“…18 O P value that is greater than isotopic equilibrium (Pfahler et al, 2013). This is especially true in acidic lowland tropical soils, in which acid phosphatase predominates compared to alkaline phosphatase (Turner, 2010), since the isotopic fractionation induced by acid phosphatase is 20e30‰ smaller than the one induced by alkaline phosphatase (Von Sperber et al, 2014).…”

“…18 O P values in the L þ plots (Fig 2, p < 0.05) may reflect the release of P from structural organic P compounds in plant leaves, which were shown to be isotopically enriched relative to isotopic equilibrium, with remarkably high d 18 O P values (up to 68‰) (Pfahler et al, 2013). Such high values were attributed to different isotopic disequilibrium metabolic process that produce isotopically enriched organic phosphates and, to a lesser extent, to the isotopic enrichment of the leaf water in comparison to the water in the soil.…”

Multi-factorialin vivostable isotope fractionation: causes, correlations, consequences and applications

“…However, as the drinking water is certainly the main but not the sole source of cell water [30,40] and as the oxygen isotope exchange of phosphate with water may also not always attain isotope equilibrium, artefacts must be taken into consideration [79]. So, plants can have different phosphate pools, in which individual approaches to oxygen isotopic equilibration with water are observed [80]. Even the pre-treatment of the samples is of importance [81].…”

Oxygen isotopes of phosphate and soil phosphorus cycling across a 6500 year chronosequence under lowland temperate rainforest

“…Specifically, rapid intracellular P cycling via pyrophosphatase results in δ 18 O P values that reflect equilibrium with cell water and temperature (Paytan et al, 2002, Blake et al, 2005, Pfahler et al, 2013, while extracellular enzymes (e.g. acid or alkaline phosphomonoesterase, phosphodiesterase, or phytase) that catalyze the hydrolysis of organic P are expected to imprint kinetic isotopic signatures specific to each substrate and enzyme (Liang and Blake, 2006a, b;von Sperber et al, 2014).…”