Salt tolerance in Eucalyptus spp.: identity and response of putative osmolytes

Abstract

In four species of salt-tolerant eucalypts ( Eucalyptus raveretiana, E. spathulata, E. sargentii and E. loxophleba ), we found substantial concentrations of quercitol -a cyclitol known for its accumulation in seeds of Quercus . Quercitol was absent in old foliage of E. globulus, a species noted for greater susceptibility to salinity, and also absent in the moderately tolerant E. camaldulensis , but, relative to other species, both had higher foliar concentrations of inositol. Simple sugars and cyclitols accumulated to osmotically significant concentrations in all species. The osmotic potential of expressed sap was always less than that of the external 'soil' solution and increasing salinity produced predictable reductions in growth and increases in ion concentrations in foliage of saplings of four eucalypt species. The more salt-tolerant species, E. spathulata, E. loxophleba and E. sargentii , were able to maintain well-regulated leaf Na ). By contrast, E. globulus was unable to exclude Na + + + + when exposed to higher NaCl concentrations (e.g. 200 and 300 mol m ----3 ). Carbon isotope signatures of foliage reflected imposed salinity but were not strongly enough correlated with growth to support previous suggestions that isotope discrimination be a means of evaluating salt tolerance. On the other hand, patterns of sugar and cyclitol accumulation should be further explored in eucalypts as traits contributing to salt tolerance, and with potential use as markers in breeding programmes.

Metabolomics demonstrates divergent responses of two Eucalyptus species to water stress

“…In addition to the well-known occurrence of proto-quercitol and viboquercitol (Figs. 2, 5, see also : Plouvier 1963;Adams et al 2005;Merchant and Adams 2005;Merchant et al 2006a, b;Arndt et al 2008), all E. dumosa contained two cyclohexanepentol stereoisomers (RI -1764 and 1871), while in a minority of E. dumosa we also detected trace amounts of epi-quercitol and another cyclohexanepentol stereoisomer (RI -1768). The occurrence of more than two stereoisomers ought not be that surprising given that the cyclohexanepentol family comprises 16 stereoisomers and plants often contain multiple stereoisomers (e.g.…”

“…pinitol, ononitol) tend to increase under salt stress and lead to osmotic adjustment (Sanchez et al 2010). In contrast, in many Eucalyptus concentrations of proline are very small, do not necessarily increase under drought and never account for more than a few percent of total osmotic potential (Marsh and Adams 1995;Adams et al 2005;Merchant et al 2006b;Warren et al 2007). Instead, leaves of some (but not all) Eucalyptus contain large constitutive amounts of the cyclohexanepentol proto-quercitol Merchant et al 2006b;Arndt et al 2008), but increases in proto-quercitol due to drought tend to be small and thus its role (if any) in osmotic adjustment is unclear.…”

“…Adams et al 2005;Merchant et al 2006b;Warren et al 2007). Here we build on this earlier literature by using a metabolomic approach to examine the response of leaf metabolites and water relations to a 2-month water stress treatment and subsequent re-watering.…”

Endogenously Synthesized (−)-proto-Quercitol and Glycine Betaine Are Principal Compatible Solutes ofSchizochytriumsp. Strain S8 (ATCC 20889) and Three New Isolates of Phylogenetically Related Thraustochytrids

“…The only other optically active cyclohexanepentol found in nature is (Ϫ)-vibo-quercitol (1L-1,2,4/3,5) of the evergreen shrub Viburnum tinus (references 37 and 51 and references therein). It should be noted that both stereoisomers of proto-quercitol are sometimes simply called quercitol; for example, it has been reported that saltand drought-tolerant species of eucalyptus accumulate quercitol (1,39).…”

Variations saisonnières des hydrates de carbone, des cyclitols et des relations hydriques chez 3 espèces d’Eucalyptus de taxonomie contrastée, en plein champ et poussant sur un site commun

“…Soluble carbohydrates were extracted according to Adams et al (2005) via a phase separation technique using 1 mL of hot methanolchloroform-water (MCW, 12:5:3).…”