Partitioning of phosphorus between biochemical and storage compounds in leaves follows a consistent pattern across four Australian genera growing in native settings

The aims of this study were to (i) assess how the P concentration in leaves of common Australian native plant species varies across a broad geographic region that includes naturally low to naturally high P status soils; and (ii) investigate whether there is a connection between P speciation and P concentration in these leaves. An ecological transect along the western edge of the Great Dividing Range was sampled for soil and leaf material of four genera (Acacia, Callitris, Einadia and Eucalyptus). Soil and leaf samples were analysed for total P, while 31P nuclear magnetic resonance (31P NMR) spectroscopy was used to determine P speciation in leaves. Soil P concentration was influenced by parent material, with soils developed on basalt particularly high in P. Leaf P concentration also varied, but this variation was poorly correlated with soil P concentration. Solution 31P NMR demonstrated uniformity in biochemical partitioning of leaf P. Concentrations of ‘biochemical’ organic P (phospholipid-P and RNA-P) in leaves were relatively constant at 200–300 mg kg−1, while concentrations of ‘storage’ P forms (orthophosphate-P and phytate-P) increased with increasing total leaf P concentration and reached values >2000 mg kg−1. These findings improve understanding of P cycling in native Australian ecosystems. Adaptation to the highest P sites resulted in accumulation of storage P forms, rather than down-regulating P uptake. At most sites, plants act as P pumps, shifting sparsely available P into the topsoil, by accumulating more P than they need and eventually shedding it in litter.