Extraradical mycelium of the arbuscular mycorrhizal fungus Glomus lamellosum can take up, accumulate and translocate radiocaesium under root‐organ culture conditions

Abstract

Radiocaesium enters the food chain when plants absorb it from soil, in a process that is strongly dependent on soil properties and plant and microbial species. Among the microbial species, arbuscular mycorrhizal (AM) fungi are obligate symbionts that colonize the root cortex of many plants and develop an extraradical mycelial (ERM) network that ramifies in the soil. Despite the well-known involvement of this ERM network in mineral nutrition and uptake of some heavy metals, only limited data are available on its role in radiocaesium transport in plants. We used root-organ culture to demonstrate that the ERM of the AM fungus Glomus lamellosum can take up, possibly accumulate and unambiguously translocate radiocaesium from a 137Cs-labelled synthetic root-free compartment to a root compartment and within the roots. The accumulation of 137Cs by hyphae in the root-free compartment may be explained by sequestration in the hyphae or by a bottleneck effect resulting from a limited number of hyphae crossing the partition between the two compartments. Uptake and translocation resulted from the incorporation of 137Cs into the fungal hyphae, as no 137Cs was detected in mycorrhizal roots treated with formaldehyde. The importance of the translocation process was indicated by the correlation between 137Cs measured in the roots and the total hyphal length connecting the roots with the labelled compartment. 137Cs may be translocated via a tubular vacuolar system or by cytoplasmic streaming per se.

No Significant Contribution of Arbuscular Mycorrhizal Fungi to Transfer of Radiocesium from Soil to Plants

“…Cs uptake and translocation by an AMF have been demonstrated in vitro with root organ cultures in which carrier-free 134 Cs was added to a liquid medium with a very low concentration of K (6). This system precludes the verification of transfer from fungus to host plant due to the lack of shoots and the difficulties associated with precise localization of Cs, which may be contained exclusively within intraradical fungal structures.…”

Effects of arbuscular mycorrhizal fungi on caesium accumulation and the ascorbate-glutathione cycle of Sorghum halepense

“…AMF have been introduced into phytoremediation of soil contaminated with radionuclides to enhance plat resistance and capacity to accumulate radionuclides. Declerck et al demonstrated that the extraradical hyphal network of AMF incorporate and translocate radiocaesium from a radiocaesium labelled root-free compartment to a root compartment, using a monoxenic multicompartment growing system 18 . De Boulois et al suggested that there was the possibility, although limited, of radiocaesium accumulation in the intraradical mycelium 19 .…”

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

“…The role of AM fungi in Cs acquisition and accumulation by plants were also investigated, but most often yielded contradictory results (see [10] and references therein).…”

“…In 2003 [10], Declerck et al unambiguously demonstrated that AM fungi could take up and translocate Cs in vitro using the two-compartment system of Rufyikiri et al [5] (see above). The total uptake of Cs represented 1.5% of the initial Cs present in the hyphal compartment (HC).…”