Use of mycorrhizal fungi for the phytostabilisation of radio-contaminated environment (European project MYRRH): Overview on the scientific achievements

Abstract

Abstract. Because plants significantly affect radionuclides (RN) cycling and further dispersion into the biosphere, it is important to understand the biological factors influencing RN plant uptake, accumulation and redistribution. In this respect, mycorrhizal fungi are of particular interest. The effects of ecto-mycorrhizal (ECM) and arbuscular mycorrhizal (AM) fungi on the transport of uranium (U) or radiocaesium (Cs) were investigated both under pot and in vitro culture conditions. Results obtained in vitro demonstrated that AM hyphae can take up and translocate U and Cs towards roots, while this uptake and translocation were not perceptible using pot culture systems with soil. These contrasting results could be due to different experimental conditions, including the K level in the external solution and the bio-availability of Cs. The in vitro studies also indicated that root colonisation by AM fungi might limit U and Cs root transport. Under pot culture conditions, they appeared to significantly reduce root to shoot translocation of U. Under the same conditions, ECM transport of Cs was demonstrated, and appeared to be dependent on fungal species. A better estimation of the potential use of mycorrhizal fungi for the phytoremediation of RN-contaminated areas is now available and will be further discussed.

Role and influence of mycorrhizal fungi on radiocesium accumulation by plants

“…Joner et al (2004) concluded that arbuscular mycorrhizas are unlikely to play any significant role in plant radiocesium acquisition through the process of fungal transport, especially in agricultural ecosystems. However, Dupré de Boulois et al (2005b) suspected that the uptake of radiocesium by AM fungi in this study could have been strongly impaired by the sorption capacity of clay, the bio-availability of K in the soil solution and/or plant K nutritional status.…”

Transport of radiocaesium by arbuscular mycorrhizal fungi to Medicago truncatula under in vitro conditions

“…The inconsistency between these experiments is probably related to the influence of soil constituents and of K on bioavailability of Cs (Delvaux et al ., 2001), root uptake of Cs (Hampton et al ., 2005) and plant accumulation of Cs (Zhu et al ., 2000). Furthermore, transport of Cs by AM fungi, and especially uptake at the level of K/Cs transporters, is probably also influenced by K as hypothesized by Dupré de Boulois and colleagues (2005a). In addition to these physiological aspects, the sterility in the compartmented pot systems could not be guaranteed and the impact of undesirable microorganisms on the bioavailability of Cs could therefore not be excluded.…”

“…Studies on the biogeochemical cycle of Cs in forest ecosystems have clearly shown that ectomycorrhizal fungi can accumulate significant amounts of Cs both in their fruiting bodies and in below‐ground mycelium (Nikolova et al ., 1997; Steiner et al ., 2002). In contrast, mycorrhiza‐mediated accumulation and transport of Cs remains uncertain or even controversial in ecosystems dominated by herbaceous plants, which are mainly colonized by AM fungi (Dupré de Boulois et al ., 2005a). Earlier studies suggested that the accumulation of Cs in mycorrhizal plants was either reduced (Dighton and Terry, 1996; Berreck and Haselwandter, 2001), similar (Rogers and Williams, 1986; Rosén et al ., 2005) or increased (McGraw et al ., 1979; Dighton and Terry, 1996; Entry et al ., 1999; Rosén et al ., 2005) as compared with non‐mycorrhizal plants, depending on the plant and AM fungal species considered.…”

Influence of silver and titanium nanoparticles on arbuscular mycorrhiza colonization and accumulation of radiocaesium in Helianthus annuus

“…radionuclide uptake by plants (Dupre de Boulois et al, 2008). Nanoparticles became of interest relatively recently, mostly because of their possible use in diverse technologies.…”