AOBPreview originally published online on January 10, 2005
Annals of Botany 2005 95(4):609-618; doi:10.1093/aob/mci066
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Annals of Botany 95/4 © Annals of Botany Company 2005; all rights reserved
Effects of Three Nickel Salts on Germinating Seeds of Grevillea exul var. rubiginosa, an Endemic Serpentine Proteaceae
1 Laboratoire de Biologie et de Physiologie Végétales Appliquées, Université de Nouvelle-Calédonie, BP 4477, 98847 Nouméa cedex, New Caledonia, 2 Laboratoire Dynamique et Ressources du Végétal, Equipe Biodiversité et Environnement, Université de Provence, Case 17, 3 pl. V. Hugo, 13331 Marseille Cedex 3, France and 3 SCME, Université de Provence, 3 pl. V. Hugo, 13331 Marseille Cedex 3, France
* For correspondence. E-mail virginieleon{at}yahoo.fr or leon{at}univ-nc.nc
Received: 12 August 2004 Returned for revision: 28 October 2004 Accepted: 23 November 2004 Published electronically: 10 January 2005
• Background and Aims Serpentine soils are usually quite infertile, arid and toxic, mainly because they contain high levels of heavy metals such as Ni. The aim of the present work was to assess the effects of Ni on the germinating seeds of Grevillea exul var. rubiginosa, an endemic serpentine Proteaceae of New Caledonia. In addition, the distribution of macronutrients and the Ni levels in germinating seeds were examined.
• Methods Seeds were sown in glass Petri dishes and exposed to increasing concentrations of Ni (5 to 500 mg Ni L–1) using Ni chloride, Ni sulphate and Ni acetate. The germination percentage and root length were measured after 40 d. Longitudinal frozen sections of germinating seeds growing in the presence of Ni (500 mg L–1 for all three salts) were used for X-ray microanalysis and X-ray elemental mapping using scanning electron microscopy (SEM).
• Key Results Ni chloride resulted in the greatest reductions in germination and root growth, particularly at 500 mg L–1, followed by Ni sulphate and Ni acetate. SEM images revealed Ca crystalline structures in the seed coat for all the samples. S/Ca and Mg/P/K/Mn were found to be distributed differently in Ni-treated samples, whereas they all followed the same pattern in the controls. For all three salts, the Ni added to the medium had accumulated in the seed coat, whereas the endosperm seemed to be devoid of Ni.
• Conclusions It is assumed that the seed coat is able to reduce the amount of Ni entering the seed, and that a high level of Ni induced the mobilization of macronutrients.
Key words: Ni, SEM, energy dispersive spectrometry (EDS) microanalysis, macronutrient mapping, seeds, Ca crystals, serpentine, Proteaceae