The extent and applications of metal accumulation and hyperaccumulation in Philippine plants

Abstract

To examine the potential applications of hyperaccumulator plants in the Philippines, we reviewed current data on the extent of metal hyperaccumulation in native species and partitioning of metals within the plant tissue. Twenty-eight species had reported tissue concentrations above the hyperaccumulator threshold, 11 species were endemic to the Philippines. Nickel was present in higher concentrations in the aboveground tissue than in the belowground tissue, but the reverse was found for copper, aluminium and chromium. The fact that copper accumulates belowground rather than above, and most hyperaccumulators of nickel identified were trees, has implications for the potential of phytoextraction using native Philippines flora.

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SHORT COMMUNICATION
https://doi.org/10.1071/BT23070
The extent and applications of metal accumulation and
hyperaccumulation in Philippine plants
Sarah DuddiganA,*, Marilyn O. QuimadoB, Edwino S. FernandoBand Mark TibbettA
For full list of author affiliations and
declarations see end of paper
*Correspondence to:
Sarah Duddigan
Department of Sustainable Land
Management, Centre for Agri-
Environmental Research and Soil Research
Centre, School of Agriculture, Policy and
Development, University of Reading,
Reading, Berkshire, UK
Email: s.duddigan@reading.ac.uk
Handling Editor:
Garry Cook
Received: 29 August 2023
Accepted: 20 November 2023
Published: 7 December 2023
Cite this:
Duddigan S et al. (2023)
Australian Journal of Botany,71(8), 537–545.
doi:10.1071/BT23070
© 2023 The Author(s) (or their
employer(s)). Published by
CSIRO Publishing.
ABSTRACT
To examine the potential applications of hyperaccumulator plants in the Philippines, we reviewed
current data on the extent of metal hyperaccumulation in native species and partitioning of metals
within the plant tissue. Twenty-eight species had reported tissue concentrations above the
hyperaccumulator threshold, 11 species were endemic to the Philippines. Nickel was present in
higher concentrations in the aboveground tissue than in the belowground tissue, but the reverse
was found for copper, aluminium and chromium. The fact that copper accumulates belowground
rather than above, and most hyperaccumulators of nickel identified were trees, has implications
for the potential of phytoextraction using native Philippines flora.
Keywords: bioaccumulation factor, hyperaccumulator, metal tolerance, metallophyte, Philippine
flora, phytoextraction, phytomining, phytoremediation, translocation factor.
Introduction
The Philippines is the fifth richest country in mineral resources worldwide, including
nickel, copper, chromite and gold (Maddox et al. 2019), and mining activity is extensive
in the region as a result. The ultramafic areas in the Philippines account for about 5% of
its estimated total land area of 298 170 km2 (Baker et al. 1992). Ultramafic areas are
often deficient in essential macronutrients (e.g. phosphorus, potassium and calcium) and
have high concentrations of potentially phytotoxic elements (e.g. magnesium, iron,
nickel, cobalt and chromium). These conditions are normally adverse to plant growth
(Galey et al. 2017). However, some plants called ‘metallophytes’ have an ability to
tolerate metal toxicity and survive and reproduce in these environments (Whiting et al.
2004; Baker and Whiting 2008). Plant species that evolved on ultramafic soils are
generally metal tolerant. Such native species could be an important source of metal-
tolerant and accumulator plants that are most likely to be able to survive the edaphic and
climatic conditions of locally contaminated lands (Carvalho et al. 2013; Claveria et al.
2019a, 2020; De Castro et al. 2020). Metallophytes are able to grow in soils with high heavy
metal concentrations through two different strategies, namely, avoidance and tolerance
(Baker 1981). Avoidance is achieved when the plant invests in external mechanisms to
keep metals chelated outside of the plant tissue (Claveria et al. 2010; Carvalho et al.
2013). Whereas tolerance is developed through physiological adaptations to accumulate
metals in high concentrations in the plant biomass.
Tolerance can be achieved through exclusion or hyperaccumulation (Jaffré et al. 1976).
Exclusion means there is limited translocation from the roots of the plant to the shoots
(Hunt et al. 2014; Lange et al. 2017; Sanqui et al. 2020). Hyperaccumulators, have
evolved the capability to accumulate certain metal elements in their shoots, especially the
leaves, at concentrations 100× greater than those typically measured in shoots of the
common non-accumulator plants (Jaffré et al. 1976; Brooks et al. 1977, 1998). Reeves
(1992) stated that concentrations must be recorded in the dry matter of any aboveground
tissue in at least one specimen growing ‘in its natural habitat’, i.e. not under artificial
conditions, such as through metal-salt amendments to an experimental soil or hydroponic
nutrient solutions (van der Ent et al. 2013). More than 700 hyperaccumulating plants have