Nickel biopathways in tropical nickel hyperaccumulating trees from Sabah (Malaysia)

Abstract

The extraordinary level of accumulation of nickel (Ni) in hyperaccumulator plants is a consequence of specific metal sequestering and transport mechanisms, and knowledge of these processes is critical for advancing an understanding of transition element metabolic regulation in these plants. The Ni biopathways were elucidated in three plant species, Phyllanthus balgooyi, Phyllanthus securinegioides (Phyllanthaceae) and Rinorea bengalensis (Violaceae), that occur in Sabah (Malaysia) on the Island of Borneo. This study showed that Ni is mainly concentrated in the phloem in roots and stems (up to 16.9% Ni in phloem sap in Phyllanthus balgooyi) in all three species. However, the species differ in their leaves – in P. balgooyi the highest Ni concentration is in the phloem, but in P. securinegioides and R. bengalensis in the epidermis and in the spongy mesophyll (R. bengalensis). The chemical speciation of Ni2+ does not substantially differ between the species nor between the plant tissues and transport fluids, and is unambiguously associated with citrate. This study combines ion microbeam (PIXE and RBS) and metabolomics techniques (GC-MS, LC-MS) with synchrotron methods (XAS) to overcome the drawbacks of the individual techniques to quantitatively determine Ni distribution and Ni2+ chemical speciation in hyperaccumulator plants.

Growth effects in tropical nickel‐agromining ‘metal crops' in response to nutrient dosing

“…In their native habitats, P. rufuschaneyi and R. cf. bengalensis occur on degraded ultramafic soils with extremely low available nutrients (van der Ent and Mulligan, 2015; Bouman et al, 2018;van der Ent et al, 2018). Hence, in situations when biomass production is not a priority (e.g., for phytoremediation purposes), these species can be employed without fertilizer application.…”

“…Brearley (2005) found that P is one of the limiting nutrients for Dryobalanops lanceolata in a nutrient limitation experiment using a Malaysian ultramafic soil. We expected significant growth responses to P addition because of the limited mobility of P in soils (Nye and Tinker, 1977) and the extremely low P concentrations in highly weathered tropical ultramafic soils (Proctor, 2003;van der Ent et al, 2018). Elsewhere, pot experiments and field trials have shown positive responses of tropical forest tree seedlings to P (Burslem et al, 1995;Lawrence, 2001;Cai et al, 2008).…”

“…In tropical regions, there are unrealised opportunities for economic Ni agromining as the ultramafic outcrops are extensive and are often coupled with high occurrence of Ni hyperaccumulator plant species ( Reeves et al, ; van der Ent et al, ; Nkrumah et al, ). Notably, some of the newly discovered ‘hypernickelophores' in the tropics are among the potentially most useful for agromining globally ( van der Ent and Mulligan , ; Nkrumah et al, , , ; van der Ent et al, ; ). However, the agronomic systems required for viable commercial Ni agromining have not been previously tested for these potential ‘metal crops'.…”

“…bengalensis (with up to 1.2% Ni), Actephila alanbakeri (with up to 1.4% Ni), Dichapetalum gelonioides subsp. tuberculatum (with up to 1.8% Ni), and Antidesma montis-silam (with up to 1.6% Ni) (van der Ent and Mulligan, 2015;van der Ent et al, 2016avan der Ent et al, , 2017Nkrumah et al, 2018cNkrumah et al, , 2018d. Phyllanthus rufuschaneyi and R. cf.…”

Rock-type control of Ni, Cr, and Co phytoavailability in ultramafic soils

“…Whittaker 1954;Main 1974;Main 1981;Galey et al 2017;Gonneau et al 2017;Van der Ent et al 2017;Van der Ent et al 2018). Although knowledge about relationships between metals with other elements or factors in plants is broad, it is still difficult to final identify the causes of differences in Ni, Cr, and Co content in plants from Polish ultramafic soils.…”