Contrasting phosphorus (P) accumulation in response to soil P availability in 'metal crops' from P-impoverished soils

Background and aims Phosphorus is one of the major nutrients that directly or indirectly affects all aspects of plant growth. Tropical nickel hyperaccumulators, including Phyllanthus rufuschaneyi and Rinorea cf. bengalensis from Borneo Island (in the Malaysian state of Sabah), have evolved to grow in extremely P-impoverished ultramafic soils. This study aimed to establish the response of the root and shoot ionome of these two agromining 'metal crops' to soil P availability. Methods We undertook a soil P dosing trial on P. rufuschaneyi and R. cf. bengalensis in Sabah (Malaysia) over a period of 12 months. We measured the elemental concentrations in the soil solution and roots, as well as in the developed and developing stems and leaves. Results The results show that root and shoot P accumulation increased markedly as soil P availability increased by 80-fold in P. rufuschaneyi, whereas R. cf. bengalensis did not increase as strongly to P supply, despite a 135-fold increase in soil solution P. The contrasting observations on the root and shoot P accumulation patterns in these species suggests distinct P acquisition strategies in these species. The non-responsiveness of R. cf. bengalensis to increasing soil P availability may be related to its possible association with mycorrhizal fungi. Conclusion The findings of this study reveal the complexities of phosphate uptake, transport and accumulation in these 'metal crops'. This information is essential to develop appropriate nutrient management in nickel agromining operations.