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

Is chromium (III) possible to be phytoremediated by
Solanum nigrum L.? The beginning…
P. Ferraz, F. Fidalgo and J. Teixeira
Biology Department, Faculty of Sciences, University of Porto, Portugal.
The environmental pollution caused by heavy metals is, nowadays, a major ecological
problem with disastrous future consequences to our planet. This problem affects all living
organisms, from bacteria to animals, including humans. Therefore, there is a growing
awareness of this fact, which led to the action of several health authorities worldwide. One of
the emerging technologies to solve this problem is phytoremediation, the use of plants and
their associated microbes for environmental cleanup [1]. This technology has gained
acceptance in the past 15 years as a cost-effective and noninvasive alternative for engineeringbased
remediation methods. 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 chromium (III), which is a highly toxic environmental pollutant.
Thus, to verify the effect of chromium (III) on S. nigrum development, seeds were surface
sterilized and incubated in a sterile nutrient solution (Hoagland solution [3]), supplemented
with increasing concentrations of Cr (III): 0 µM, 125 µM, 250 µM, 375 µM and 500 µM. At
the end of the fourth week, several seedling biometric parameters were assessed. Significant
decreases on fresh weight and root length could be observed starting from the 375 µM
treatment, whilst the shoot length significantly decrease only in the 500 µM treatment.
Control-derived seedlings were grown hydroponically for four weeks in Hoagland solution
under 3 different situations: one set without Cr (III); another one exposed to 375 µM Cr (III);
and the third consisted on a short shock treatment with 1000 µM Cr (III) throughout the last
week. After this period, at least 3 plants from each growth condition were used for the
determination of several biometric aspects. Roots and shoots from plants were frozen under
liquid N2, grinded to a fine powder and stored at -80ºC for future processing. It was possible to
observe that there were no significant variations in root and shoot fresh and dry weight, length
and water content, for both chromium (III) treatments.
These preliminary results reveal that S. nigrum can tolerate very high concentrations of
chromium (III) in the rhizosphere. To further discriminate if this tolerance is due to a enhanced
capacity to exclude this metal or to bioaccumulate it in plant tissues, the next approach will
consist on chromium (III) quantifications on roots and shoots of the stored plant material.
Future studies will also be performed to evaluate the degree of stress that plants are subjected
when exposed to high concentrations of chromium (III), 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
262 3 rd meeting of young researchers at UP