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Master Thesis

Interactions entre mycorhization, nutrition en phosphore et adaptation de la plante à la toxicité du nickel sur substrat ultramafique. Vers une optimisation de la mycorhization d'Alphitonia neocaledonica

Abstract : The main objective of this work was to determine the optimal concentration of phosphorus leading to the best mycorrhization of Alphitonia neocaledonica on ultramafic (UF) topsoil. The experiment was conducted at the University of New Caledonia, Noumea, between March and September 2012. Five concentrations were tested (0 ; 0,2 ; 0,5 ; 1 ; 2 t.ha-1 Superphosphate Triple (ST)), spread over 100 plants inoculated and 100 plants non-inoculated, placed on the UF topsoil in controlled irrigation. Plant growth, rate of mycorhization (%M) and sporulation were followed during one year. At the end of the experiment, biomass (fresh and dry) was measured and the mineral and metal concentrations were determined by atomic absorption spectrometer. The optimum of %M (18% ±2) and sporulation (5200 ±890 spores/100g of dry soil) were obtained for a ST concentration of 1t.ha-1 (210kg.ha-1 P, P3). At this concentration, a significant positive MGR (mycorrhizal growth response) was observed (+2.1 cm). Likewise, a rebalancing of the Ca/Mg ratio and an improvement of P and K absorption (correlated to the %M, r ²=0,91 in the roots) were measured in inoculated plants. Concentrations of Ni, Co and Cr have been significantly reduced in root by mycorrhization but translocation to the aerial parts of these elements is increased by mycorrhization (resp. x1,5 - x32 - x41 in P3). Finally, a higher water content was measured in inoculated plants (+12% H20 in P3), with a maximum in P0 (+25% H20). The absence of N and K fertilization in P0 seems to be the cause of this difference between P0 and P3. In conclusion, our studies highlight that an optimal concentration of 1t.ha-1of ST can be made to maximize the mycorrhization of A. neocaledonica on UF topsoil. It will now be necessary to determine which are the consequences of these amendments on scrubland ecosystems because the phosphorus lack is a very limiting factor of the mycorrhizal symbiosis down there
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Master Thesis
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Antoine Pierart. Interactions entre mycorhization, nutrition en phosphore et adaptation de la plante à la toxicité du nickel sur substrat ultramafique. Vers une optimisation de la mycorhization d'Alphitonia neocaledonica. Sciences agricoles. 2012. ⟨dumas-00745807⟩

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