Different response of perennial ryegrass-Epichloë endophyte symbiota to the elevated concentration of heavy metals in soil.

The phenomenon of plant mutualistic symbiosis with microbes may have a positive effect on the improvement of plant tolerance to environmental stresses as well as on the ability of plants to accumulate heavy metal (HM) ions from soil. The influence of Epichloë fungal endophyte (Ascomycota, Clavicipitaceae) on perennial ryegrass (Lolium perenne L.) plants grown in the presence of elevated concentrations of HM ions (Cd2+, Pb2+, and Cu2+) in soil was studied. The presence of Epichloë in the host grass tissues resulted in different accumulation of HM ions in the aboveground parts of the plants. In some cases, endophyte infection positively affected ryegrass ability to accumulate HM ions from soil. In plants with (E +) and without (E -) endophytes, the hormesis effect was induced by the elevated concentration of Cu2+ ions, resulting in better growth and photosynthesis, as examined by measurements of Chl a fluorescence. The obtained results indicate that based on the laboratory evaluation of the efficiency of HM accumulation, we were able to choose the best associations of perennial ryegrass with endophytes for HM phytoremediation.

Chlorophyll a fluorescence in evaluation of the effect of heavy metal soil contamination on perennial grasses.

Chlorophyll a fluorescence gives information about the plant physiological status due to its coupling to the photosynthetic electron transfer chain and to the further biochemical processes. Environmental stresses, which acts synergistically, disturbs the photosynthesis. The OJIP test, elaborated by Strasser and co-workers, enables comparison of the physiological status of plants grown on polluted vs. control areas. The paper shows that the Chl a measurements are very useful tool in evaluating of heavy metal ions influence on perennial grasses, tested as potential phytoremediators. Among 5 cultivars tested, the highest concentration of Cd and Zn ions, not associated with the yield reduction, was detected in the biomass of tall fescue cv. Rahela. Chl a fluorescence interpreted as double normalized curves pointed out Rahela as the outstanding cultivar under the HM ions stress.