3rd meeting of young researchers at UP 1 - IJUP - Universidade do ...

Can Solanum nigrum L. be use to phytoremediate
nickel-polluted sites? The first steps…
P. Ferraz, F. Fidalgo and J. Teixeira
Biology Department, Faculty of Sciences, University of Porto, Portugal.
Contamination by heavy metals in ecosystems poses major environmental problems worldwide
with substantial economical and health hazard consequences. Phytoremediation - the use of
plants and their associated microbes to remove or immobilise contaminants [1] - may offer a
low cost method for the remediation of heavy metals-contaminated soils. Various
phytoremediation strategies are possible, with different phytotechnologies profiting from
different plant properties. Concerning metal contamination of soils, specifically, the main
treatment streamlines are phytoextraction and phytostabilisation. Solanum nigrum L. is a plant
species that has been reported to hyperaccumulate heavy metals such as cadmium and zinc, and
has the particularity of being a fast growing, easily adaptable and having a greater biomass
than most hyperaccumulators [2], making it a potential candidate for phytoremediation and for
the accumulation of other metals, such as nickel, which is a plant micronutrient and at the same
time an environmental pollutant. It is well known that most of the micronutrients can be
phytotoxic if when present in the rooting medium at elevated concentrations.
Thus, to assess the effect of nickel on S. nigrum, seeds were surface sterilized and incubated in
a sterile nutrient solution (Hoagland solution [3]), supplemented with increasing concentrations
of nickel: 0 µM, 0.5 µM, 7.5 µM, 30 µM, 50 µM and 100 µM. After 4 weeks of exposure,
several seedling biometric parameters were assessed and significant decreases on fresh weight
and root length could be observed starting from the 7.5 µM treatment, whilst the shoot length
significantly decrease only in the 100 µM treatment.
Subsequently, plants were grown hydroponically for four weeks in Hoagland solution under 3
different situations: one set without Ni; another one exposed to 7.5 µM Ni; and the third
consisted on a short shock treatment with 100 µM Ni throughout the last week. After this
period, at least 3 plants from each growth condition were frozen under liquid N2, grinded to a
fine powder and stored at -80ºC for future processing. Several biometric parameters were
analyzed and it was possible to observe a significant decrease in root and shoot fresh weight
and length, in shoot dry weight, with a significant parallel increase in water content, for both
treatments.
These preliminary results reveal that the exposure to nickel concentrations ≥ 7.5 µM cause
deleterious effects to the plants, thus suggesting that this metal is detrimental to them. The next
step in this study will consist on nickel quantifications on roots and shoots of the stored plant
material in order to assess this plant species’ nickel phytoremediation potential. Future studies
will also be performed to evaluate the degree of stress that plants are subjected when exposed
to high concentrations of nickel, both at the biochemical and molecular levels.
[1] Pilon-Smits E. 2005. Phytorremediation. Annu. Rev. Plant Biol. 56: 15-39
[2] Marques, A.P.G.C., Oliveira, R.S., Rangel, A.O.S.S., Castro, P.M.L. (2006) Zinc accumulation in Solanum
nigrum is enhanced by different arbuscular mycorrhizal fungi. Chemosphere 65 (7): 1256-1263
[3] Taiz L, Zeiger, E. 2006. Plant Physiology. 4th edition. Sinauer Associates, Inc.USA
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