Lemcoff, J.H., IFEVA(CONICET-FAUBA), Departamento De Biología Aplicada Y Alimentos, Universidad De Buenos Aires, Av. San Martín 4453, 1417 Buenos Aires, Argentina, Departamento De Producción Vegetal, Facultad De Agronomía, Universidad De Buenos Aires, Argentina
Guarnaschelli, A.B., IFEVA(CONICET-FAUBA), Departamento De Biología Aplicada Y Alimentos, Universidad De Buenos Aires, Av. San Martín 4453, 1417 Buenos Aires, Argentina, Departamento De Producción Vegetal, Facultad De Agronomía, Universidad De Buenos Aires, Argentina
Garau, A.M., IFEVA(CONICET-FAUBA), Departamento De Biología Aplicada Y Alimentos, Universidad De Buenos Aires, Av. San Martín 4453, 1417 Buenos Aires, Argentina, Departamento De Producción Vegetal, Facultad De Agronomía, Universidad De Buenos Aires, Argentina
Prystupa, P., IFEVA(CONICET-FAUBA), Departamento De Biología Aplicada Y Alimentos, Universidad De Buenos Aires, Av. San Martín 4453, 1417 Buenos Aires, Argentina, Departamento De Producción Vegetal, Facultad De Agronomía, Universidad De Buenos Aires, Argentina

Eucalyptus camaldulensis Dehnh., considered as a drought tolerant species, was examined in relation to some mechanisms linked to drought tolerance (cell-wall elastic adjustment and osmotic adjustment) and to the intraspecific variation related to those features. Rooted cuttings of five clones obtained from three different provenances from Australia (Gilgandra: 106, 109; Lake Albacutya: 119, 125; Condamine: 105) were gradually submitted to a water limitation regime. Water stress curtailed relative leaf area growth rate, pre-dawn relative water content (RWC) and noon stomatal conductance (gs) in all clones. Shoot water parameters were estimated at the end of the drought period by pressure-volume (P-V) analysis through a repeat pressurization method. The curves obtained were analyzed by Schulte's P-V Curve Analysis Program. Drought decreased very significantly the osmotic potential at full turgor (ΨπFT) and at the turgor loss point (ΨπTLP), with a significant clone effect: 105 had the lowest values (-2.12 ± 0.04 MPa and -2.39 ± 0.05 MPa). Osmotic adjustment (OA) on average was 0.34 ± 0.02 MPa. Drought increased maximum bulk modulus of elasticity (εMAX) by 6.6 ± 0.7 MPa. There were no clonal differences in either OA or elastic adjustment. Water stress increased significantly turgor potential at full turgor (ΨFT), and differences between control and stress plants show that the OA recorded did not fully account for the positive changes in turgor of stressed plants. Drought decreased shoot turgid mass/dry mass ratio (TM/DM), again with a significant clone effect: 105 had the lowest value (2.66 ± 0.11). Reduced shoot TM/DM combined with increases in εMAX during stress were indicative of cell wall adjustment, reduced turgor-loss volumes and tightening of the cell walls around the protoplasts, suggesting a cell size reduction. No effects were observed on RWC at the turgor loss point. A regression model that considered εMAX and ΨπFT explained best the response patterns of stressed plants. The mechanisms observed in Eucalyptus camaldulensis that delay growth while maintaining turgor and water uptake allow us to consider it as a dehydration postponement species.