Abstract

Early studies in some Eucalyptus species showed different growth rate in response to water stress. In areas with low precipitations (⩽150mm per year), Eucalyptus camaldulensis Dehnh and Eucalyptus cladocalyx F. Muell showed higher plant survival and higher growth rate than Eucalyptus globulus Labill; suggesting that these species should have different adaptation mechanisms to cope drought stress. In the present study, the main goal was to determinate physiological, biochemical and molecular responses in three Eucalyptus species that differs in their tolerance to drought stress. The Eucalyptus species studied were E. globulus, E. camaldulensis and E. cladocalyx. Two water availability treatments were evaluated in five replications by species; T1 well-watered plants (-1MPa) and T2 non-watered plants (-2.8MPa). Eucalyptus plants were grown in pots under greenhouse conditions (25ºC, 16/8h day/light photoperiod). Soil water availability (%) was measured with FDR Decagon Devices (ECHO20), and recorded every 30min. by data logger (EM50). Differences were observed in stomatal conductance (gs), net photosynthetic rate (A), intercellular CO2 concentration (Ci), stem water potential (ψmd), osmoprotectors and gene expression. E. camaldulensis and E. cladocalyx showed higher osmotic adjustment than E. globulus; proline content was higher in those species in particular after 7 days under water restrictions. Similar results were observed for total soluble sugars. In addition and under drought stress treatments, quantitative Real-Time PCR analysis showed that gene expression of pyrroline-5-carboxylate synthetase (Pc5s), dehidryn (Dhn10) and CBF-like genes were best observed in E. camaldulensis and E. cladocalyx under drought stress condition. Suggesting, various mechanisms are involved in Eucalyptus drought tolerance. Acknowledgements, this research was carried out with financial support from CORFO-INNOVA (06CN12PFT-70).