No abstract

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.

The chemical composition of the leaf essential oil of Melaleuca quinquenervia (Cav.) S. T. Blake from NewCaledonia has been investigated on 133 samples collected from seven harvesting locations on the island. Forty-two components were identified by GC-MS analysis and the major ones were 1,8-cineole (0.1-76%), viridiflorol (0-67%), p-cymene (0 -40%), γ γ γ γ γ-terpinene (0-33%), α α α α α-pinene (0-30%), α α α α α-terpineol (0-24%), terpinolene (0-19%), limonene (0.1-16%) and ledol (0-21%). Viridiflorol and ledol, two sesquiterpene alcohols, were identified unambiguously by 1 H-and 13 C-NMR analyses. A sulphur compound, methylthiobenzoate, was characterized by gas chromatography-mass spectrometry (GC-MS). Niaouli essential oils from New Caledonia were classified into three chemotypes, using principal component analysis (PCA). Of these three chemotypes, found co-occurring in the harvesting locations across the island, chemotype 2, already characterized in Madagascar, is rich in 1,8-cineole (up to 80%) and is widespread (65.4% of the overall samples); chemotype 1 (24.8% of samples) is rich in terpinene derivatives; and chemotype 3 (9.8% of samples) is rich in α α α α α-pinene and viridiflorol.

Some species of the Cunoniaceae are reputed to possess medicinal properties. An investigation of 50 species of this family in New Caledonia has permitted the screening of 204 extracts (101 ethyl acetate extracts and 103 methanol extracts) for antimicrobial activities against one yeast (Candida albicans), one filamentous fungus (Fusarium oxysporum), and eight bacterial species (Erwinia carotovora, Klebsiella pneumoniae, Pseudomonas aeruginosa, Escherichia coli, Staphylococcus aureus, Staphylococcus epidermidis, Corynebacterium accolans, Bacillus subtilis).Ninety-six per cent of the plants exhibited antimicrobial activity, with a significant difference in the number of responses between fungi (18.8%) and bacteria (81.2%). Moreover, Gram +ve strains appear more sensitive than Gram -ve ones. The most active plants were Acsmithia meridionalis, A. pedunculata, Cunonia macrophylla, C. vieillardii, Pancheria alaternoides, and P. elegans. Cunonia macrophylla appears to be the best candidate for a chemical investigation using bioguided fractionation as extracts from its leaves and flowers effectively inhibited six strains (one yeast, two Gram -ve bacteria and three Gram +ve bacteria).

Grevillea exul var exul (Proteaceae), a tree species native to serpentine soils in New Caledonia, is a reported manganese accumulator. Since the metal tolerance of this species remains unknown, its growth and metal accumulation were studied for seven heavy metals under controlled conditions. Brassica juncea, a popular species for metal phytoremediation, was used as a reference. G. exul seedlings were more tolerant to Cr, Zn, Ni, and Cu than B. juncea. There were no differences in Hg, and Cd tolerance between both species. B. juncea seedlings concentrated more Cd, Hg, and Cr in their shoot than G. exul seedlings, while Ni, Zn, and Mn levels were similar for both species. Comparison then focused on tolerance at toxic doses of Ni and Mn using older individuals of both species. No growth inhibition for G. exul plants was observed, whereas the growth of B. juncea was significantly inhibited at the higher metal concentrations. Shoot Mn and Ni concentrations were again lower in G. exul plants as compared to B. juncea, suggesting a mechanism of partial Ni and Mn exclusion in G. exul. In a subsequent study, 1-year-old G. exul plants favored Ni accumulation in roots while Mn accumulated preferentially in shoots.