Metal toxicity differently affects the Iris pseudacorus-arbuscular mycorrhiza fungi symbiosis in terrestrial and semi-aquatic habitats

Phytoremediation offers an environmental friendly alternative to conventional cleanup techniques. In this study, mycorrhizal fungi isolated from the roots of Mentha longifolia grown in the basin of the Centuria River (S Poland) were used. Iris pseudacorus was grown in substratum from an industrial waste, enriched in Pb, Fe, Zn, and Cd in a terrestrial and water-logged habitat. Plant yield and photosynthetic performance was the highest in the aquatic environment; however, the presence of toxic metals (TM) negatively affected photosystem II (PSII) photochemistry as shown by the JIP test. Fungi colonization and Cd accumulation within plant tissues was decreased. In the terrestrial habitat, neither arbuscular mycorrhizal fungi (AMF) nor metal toxicity affected plant growth, although metal uptake, Cd in particular, as well as photosynthesis were affected. Inoculated plants accumulated significantly more Cd, and photosynthesis was downregulated. The results presented in this study clearly indicate that the I. pseudacorus-AMF symbiosis adapts itself to the presence of toxic metals in the environment, optimizing resource supply, energy fluxes, and possibly stress tolerance mechanisms. Plant/AMF consortia grown in terrestrial and water-logged habitats utilize different strategies to cope with metal toxicity. The use of AMF in improving the phytoremediation potential of I. pseudacorus needs, however, further research.

Mycorrhizal fungi modulate phytochemical production and antioxidant activity of Cichorium intybus L. (Asteraceae) under metal toxicity

Cichorium intybus (common chicory), a perennial plant, common in anthropogenic sites, has been the object of a multitude of studies in recent years due to its high content of antioxidants utilized in pharmacy and food industry. Here, the role of arbuscular mycorrhizal fungi (AMF) in the biosynthesis of plant secondary metabolites and the activity of enzymatic antioxidants under toxic metal stress was studied. Plants inoculated with Rhizophagus irregularis and non-inoculated were grown on non-polluted and toxic metal enriched substrata. The results presented here indicate that AMF improves chicory fitness. Fresh and dry weight was found to be severely affected by the fungi and heavy metals. The concentration of hydroxycinnamates was increased in the shoots of mycorrhizal plants cultivated on non-polluted substrata, but no differences were found in plants cultivated on metal enriched substrata. The activity of SOD and H2O2 removing enzymes CAT and POX was elevated in the shoots of mycorrhizal plants regardless of the cultivation environment. Photochemical efficiency of inoculated chicory was significantly improved. Our results indicate that R. irregularis inoculation had a beneficial role in sustaining the plants ability to cope with the deleterious effects of metal toxicity.

Mycothallic/mycorrhizal symbiosis of chlorophyllous gametophytes and sporophytes of a fern, Pellaea viridis (Forsk.) Prantl (Pellaeaceae, Pteridales)

Gametophytes of Pellaea viridis that appeared spontaneously on the surface of substratum originating from an ultramafic area were found to form mycothallic symbiosis with arbuscular mycorrhizal fungi (AMF) under laboratory conditions. In gametophytes and sporophytes grown with Glomus tenue, abundant arbuscule formation was observed at both stages. In gametophytes, the fungus was found in the region where the rhizoids are initiated. If G. intraradices was added to the soil, the gametophytes were colonised mostly by G. tenue, and roots of sporophytes were colonised by G. intraradices. The presence of AM fungi in both gametophytes and sporophytes of P. viridis resulted in the development of larger leaf area and root length of the sporophyte. The analysis of gametophytes from the Botanical Garden in Krakow (Poland) showed that cordate gametophytes of Pteridales, namely Pellaea viridis (Pellaeaceae), Adiantum raddianum and A. formosum (Adiantaceae), were also mycothallic.