Data di Pubblicazione:
2006
Citazione:
Ammonium nutrition as a strategy for cadmium mobilisation in the rhizosphere of sunflower / P. Zaccheo, L.E.V. Crippa, V. Di Muzio Pasta. - In: PLANT AND SOIL. - ISSN 0032-079X. - 283:1-2(2006 May), pp. 43-56. [10.1007/s11104-005-4791-x]
Abstract:
Ammonium nutrition of higher plants results in rhizosphere acidification due to proton excretion by root
cells. The acidification induced by ammonium-fed plants can be exploited to promote a localised metal
mobilisation in neutral to alkaline polluted soils and therefore to improve phytoextraction. The effects of
ammonium uptake by sunflower (Helianthus annuus L.) plants on the external medium pH, aerial and root
growth and tolerance to soluble Cd were studied in hydroponic culture. The ammonium-fed sunflowers
induced a strong acidification of the solution and, compared to the nitrate-fed sunflowers, a small modification
in mineral nutrition and a different Cd partitioning between root and shoot. Moreover, ammonium
nutrition was found to induce a great mobilisation of a sparingly soluble form of cadmium (CdCO3). A pot
experiment studied the ability of different ammonium-based fertilisers (ammonium sulphate, ammonium
thiosulphate, urea) to modify bulk and rhizo-soil pH, compared to the effect of calcium nitrate and to the
unfertilised soil. Furthermore, in order to promote the persistence of ammonium in soil, a combined
treatment of ammonium sulphate and DMPP, a nitrification inhibitor, was tested. Soil pH was strongly
modified by chemical and biological processes involved in fertiliser transformations. In particular, due to
nitrification, all ammonium-based treatments showed a bulk soil acidification of over 1.5 pH units and a
relative increase in rhizo-soil pH as a consequence of nitrate uptake. The treatment with DMPP showed an
opposite trend with a lower pH in rhizo-soil than in bulk soil. The ability of ammonium-fed plants to
mobilise heavy metals from the non-labile pool was studied in another pot experiment using three soils with
different properties and at different degree and type of heavy metal contamination. Whatever the soil, the
metal concentrations in shoots were higher in plants fed with ammonium (ammonium sulphate plus DMPP
treatment). Our results support the hypothesis that ammonium nutrition with nitrification inhibitors is a
viable strategy to improve heavy metals phytoextraction while protecting bulk soil from acidification and
presumably from metal leaching.
Tipologia IRIS:
01 - Articolo su periodico
Keywords:
Cadmium; DMPP; Nitrogen fertilisers; Phytoextraction; Rhizosphere acidification; Sunflower
Elenco autori:
P. Zaccheo, L.E.V. Crippa, V. Di Muzio Pasta
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