Two selected examples of PIXE microanalysis in ecophysiology are presented. Studies of heavy metal distributions in mycorrhizal and non-mycorrhizal roots of Plantago lanceolata showed different filtration mechanisms of Zn/Pb and Fe/Mn, both enabling plants to cope with metals present in the environment. Studies of the mechanism used by the beetle Chrysolina pardalina to eliminate excessive amounts of Ni revealed that Malpighian tubules are responsible for the elimination of this metal from the hemolymph.In both examples GeoPIXE software was used for true elemental mapping using the Dynamic Analysis method and analysis of spectra from selected micro-areas. Specimen thickness and matrix composition were obtained from proton backscattering spectra.

The aim of this study was to determine elemental composition of sap-feeding insects inhabiting various parts of the Ni hyperaccumulating plant Berkheya coddii Roessl., the endemic species of ultramafic outcrops in Mpumalanga, South Africa. Three species were examined: the aphid Protaphis pseudocardui (Aphididae), abundant on young leaves; the mealybug Orthesia sp. (Ortheziidae) colonizing underground parts of this plant, and the bug Norialsus berkheyae (Cixiidae) living on young shoots. Maps of Ni, K, Ca, Zn, and Fe for selected body areas of these species were generated using Dynamic Analysis method on the basis of particle-induced X-ray emission (micro-PIXE) and proton backscattering (BS) measurements. Atomic absorption spectrometry was used to determine Ni, Zn, Cu, Fe contents in the B. coddii organs, in some sapfeeding insect species including these mentioned above, and in the assassin bug hunting on Chrysolina pardalina, a monophagous beetle of B. coddii. Bioaccumulation factor for Ni in the examined species was below 0.05, and much higher for other metals (Zn ‡ 2; Fe £ 5). Ni distribution within body was species-dependent. It was the highest in the antennae of P. pseudocardui, in the head of Orthesia sp. and in the metathorax of N. berkheyae. Distribution patterns of other metals were different among examined species. Ca was recorded mainly in peripheral parts of the body in all species. Zn showed similar distribution to Ni. Fe distribution was similar to Ni only in the mealybugs. Uneven concentrations of metals within selected body regions indicated their relations with specific organs. Analysis of Ni transfer to higher trophic levels was done on the basis of two food nets: B. coddii-C. pardalina-Rhinocoris neavii and B. coddii-P. pseudocardui-Polyrhachis ant and led to the conclusion that the role of sap-feeding insects in Ni transfer was marginal.

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Grasshopper Stenoscepa sp is an insect species feeding on the South-African Ni-hyperaccumulating plants. Large amounts of Ni ingested by them have no effect on their development. To explain their ability to survive in such extreme conditions, we investigated the distribution of elements in the insect body by means of a nuclear microprobe [micro-particle induced x-ray emission (PIXE) and backscattering (BS)]. GeoPIXE II software was used for quantitative elemental mapping complemented by evaluation of data extracted from arbitrarily selected micro-areas. Micro-PIXE analysis in Stenoscepa sp tissues showed the highest Ni level in the gut and Malpighian tubules. The activity of glutathione-dependent enzymes and glutathione (GSH) content in the tissues of second-stage larvae were measured. One of the ways to survive under chronic Ni exposure conditions is an intensified GSH synthesis. GSH concentration in tissues of the grasshoppers was very high, about six times higher than in larvae of other Acrididae species from areas contaminated with heavy metals in Europe. Catalase (CAT) activity was 5-10 times lower in comparison to other Orthoptera species. Glutathione reductase (GR) activity was unexpectedly low (at the detection limit level). Likely, the studied grasshoppers may use other metabolic pathways for regeneration of the reduced form of GSH, e.g. thioredoxine system.