Sensitivity of jarrah (Eucalyptus marginata) to phosphate, phosphite, and arsenate pulses as influenced by fungal symbiotic associations

Many plant species adapted to P-impoverished soils, including jarrah (Eucalyptus marginata), develop toxicity symptoms when exposed to high doses of phosphate (Pi) and its analogs such as phosphite (Phi) and arsenate (AsV). The present study was undertaken to investigate the effects of fungal symbionts Scutellospora calospora, Scleroderma sp., and Austroboletus occidentalis on the response of jarrah to highly toxic pulses (1.5 mmol kg−1 soil) of Pi, Phi, and AsV. S. calospora formed an arbuscular mycorrhizal (AM) symbiosis while both Scleroderma sp. and A. occidentalis established a non-colonizing symbiosis with jarrah plants. All these interactions significantly improved jarrah growth and Pi uptake under P-limiting conditions. The AM fungal colonization naturally declines in AM-eucalypt symbioses after 2–3 months; however, in the present study, the high Pi pulse inhibited the decline of AM fungal colonization in jarrah. Four weeks after exposure to the Pi pulse, plants inoculated with S. calospora had significantly lower toxicity symptoms compared to non-mycorrhizal (NM) plants, and all fungal treatments induced tolerance against Phi toxicity in jarrah. However, no tolerance was observed for AsV-treated plants even though all inoculated plants had significantly lower shoot As concentrations than the NM plants. The transcript profile of five jarrah high-affinity phosphate transporter (PHT1 family) genes in roots was not altered in response to any of the fungal species tested. Interestingly, plants exposed to high Pi supplies for 1 day did not have reduced transcript levels for any of the five PHT1 genes in roots, and transcript abundance of four PHT1 genes actually increased. It is therefore suggested that jarrah, and perhaps other P-sensitive perennial species, respond positively to Pi available in the soil solution through increasing rather than decreasing the expression of selected PHT1 genes. Furthermore, Scleroderma sp. can be considered as a fungus with dual functional capacity capable of forming both ectomycorrhizal and non-colonizing associations, where both pathways are always accompanied by evident growth and nutritional benefits

Pollen and Oxygen Isotope Analyses on Late- and Post-Glacial Sediments of the Tourbière de Chirens (Dauphiné, France)

The sequence of vegetation phases in the late Glacial was studied in a sediment section from the bog Tourbière de Chirens by means of pollen analysis. 18O/16O ratios of samples of lacustrine marl, obtained from the same profile, reflect variations of 18O/16O in precipitation and thus provide an additional, independent paleoclimatic record. The observed 18O/16O variations agree well with the climatic history as deduced from pollen analysis. The climatic transition from the Oldest Dryas to the Bølling period sensu lato, as well as the beginning and end of the Younger Dryas cold phase, is marked by abrupt changes in the 18O/16O ratio which were observed also in other regions of the Alps. These drastic climatic changes probably took place simultaneously over large areas of Central Europe and occurred within short time spans

Palynostratigraphic investigation and luminescence dating of the Galgenmoos section and implications for the chronology of the last glacial cycle in the northern Alpine Foreland of Switzerland

Im Profil Huttwil-Galgenmoos liegt an der Basis ein über 2 Meter mächtiges Torfpaket, das von sandig-siltigen Sedimenten überschüttet wurde. Die klastischen Hangablagerungen fallen zeitlich in das Mittelwürm bzw. in den Übergangsbereich Hochwürm/Spätglazial. In den Torfen selber lassen sich zwei bewaldete Koniferen-Interstadiale ausgliedern. Das jüngere Interstadial wird nach palynostratigraphischen Befunden und Datierungen mit Infrarot Stimulierter Lumineszenz (IRSL) in das frühe Mittelwürm gestellt. Für das ältere Interstadial ergibt sich eine deutliche Diskrepanz zwischen den beiden verwendeten Untersuchungsmethoden. Während die IRSL-Alter für eine Zuordnung zum frühesten Mittelwürm sprechen, wird dieser Teil palynostratigraphisch in den Endabschnitt des 1. Frühwürm-Interstadials (Huttwil) gestellt. Dieses wird mit dem Brorup-lnterstadial Nordwesteuropas korreliert. Die voneinander abweichenden Ergebnisse der beiden Untersuchungsmethoden werden eingehend diskutiert.Up to 2 m of peat are found at Huttwil-Galgenmoos, central Switzerland, below a sequence of sandy and silty sediments. The elastic slope wash deposits are dated to be of Middle Wurmian and early late-glacial age, respectively. Within the peat, two interstadial periods of coniferous trees have been recognised. The younger interstadial belongs to the early Middle Wormian based oil palynological evidence and infrared stimulated luminescence (IRSL) dating. For the older interstadial, a significant discrepancy is found for the two different approaches been used. While the results of IRSL dating imply a deposition during the beginning Middle Wurmian, palynological evidences lead to a correlation with the first Wurmian-Interstadial (Brorup-Interstadial of northwestern Europe). The deviating results of the applied methods are discussed in detail