Rare Earth Elements (REEs) and Other Non-Essential Elements May Prove to Be Useful in Defining Metabolic Activity Differences Between Endophyte Infected and Endophyte-Free Tall Fescue Grasses.

This study highlights differences in the uptake of some non-essential chemical elements, namely Si and REEs, (rare-earth elements) between two tall fescue grasses, a fungal endophyte infected E(+) tall fescue grass and a related endophyte-free E(-) tall fescue grass, grown under a controlled laboratory condition. Si concentration of E(-) shoot, with a value of 873 ppm, was lower than that of the root with a value of 2,738 ppm. These concentration values are lower than the corresponding concentration values of E(+) grasses. The shoot and the root Si values of E(+) grass were 2,080 ppm and 4,060 ppm, respectively. Apparently E(+) grass assimilates more Si than E(-) grass.

Total REE (rare earth element) contents in shoots, with 91 ppb for the E(-) grass and 141 ppb for the E(+) grass, were significantly less than that in roots with 524 ppb for the E(-) grass and 753 ppb for the E(+) grass. REE distribution patterns of roots of both E(+) and E(-) grasses, constructed by normalizing the respective REE concentrations of root attached particles reveal a light REE enrichment trend with a slight positive Eu anomaly, suggesting a complexation effect at the roots for the heavy REEs which made them more mobile and thereby allowing an upward translocation of a fraction of the solution to the aboveground part or the shoot of the grass. Part of this translocation effect becomes apparent in the construction of the  REE distribution patterns of shoots normalized to REE concentrations of the roots. The REE distribution patterns of shoots normalized to their respective Root REE concentrations are marked by a concave upward pattern with a prominent Ce positive anomaly. This common pattern may be a reflection of phosphorylation effect. But the two shoot REE distribution patterns, one of E(+) grass shoot and the other of E(-) grass, presented a very clear mark of difference between them. The E(-) had a negative Eu anomaly, whereas the E(+) had a positive Eu anomaly. The significance of the difference in these anomalies has yet to be determined, but they may be attributed to differences in specific enzyme activity.        

Rb path follows K path quite closely in all natural systems. Thus K/Rb ratios may prove useful to find differences in the metabolic activity between E(+) and E(-) grasses. Shoots of the grasses are enriched in both K and Rb in comparison to the roots. The K/Rb ratios of particles that adhered to the roots had ratios between 460 and 468. In contrast, the roots themselves had K/Rb ratios between 2353 for the E(-) grass and 2109 for the E(+) grasses. The translocations of K and Rb to aboveground parts result in higher K/Rb ratios for the shoots. The K/Rb ratio of the E(+) shoot was about 3224, whereas that of the E(-) shoot was 2813. A small increase in the K/Rb ratio for the E(+) shoot as compared to the E(-) shoot suggests higher metabolic activity for the endophyte-infected grass.