ANALYSIS OF LEAF WATER RELATIONS IN LEAVES OF 2 OLIVE (OLEA-EUROPAEA)CULTIVARS DIFFERING IN TOLERANCE TO SALINITY

One-year-old rooted cuttings of olive (Olea europaea L. cvs. Frantoio and Leccino) were grown either hydroponically or in soil in a greenhou se. Plants were exposed to NaCl treatments (0, 100, and 200 mM) for 35 days, followed by 30 to 34 days of relief from salt stress to determi ne whether previously demonstrated genotypic differences in tolerance to salinity were related to water relations parameters. Exposure to hi gh salt concentrations resulted in reductions in predawn water potenti al (Psi(w)), osmotic potential at full turgor (Psi(pi FT)), osmotic po tential at turgor loss point (Psi(pi TLP)), and relative water content (RWC) in both cultivars, regardless of the growth substrate. Leaf Psi (w) and RWC returned to values similar to those of controls by the end of the relief period. The effect of salinity on Psi(pi) appeared earl ier in Leccino than in Frantoio. Values for Psi(pi FT) were -2.50, -2. 87, and -3.16 MPa for the 0, 100, and 200 mM salt-treated Frantoio pla nts, respectively, and -2.23, -2.87, and -3.37 MPa for the correspondi ng Leccino plants. Recovery of Psi(pi) was complete for plants in the 100 mM salt treatment, but not for plants in the 200 mM salt treatment , which maintained an increased pressure potential (Psi(p)) compared t o control plants. Net solute accumulation was higher in Leccino, the s alt-sensitive cultivar, than in Frantoio. In controls of both cultivar s, cations contributed 39.9 to 42.0% of the total Psi(pi FT), mannitol and glucose contributed 27.1 to 30.8%, and other soluble carbohydrate s contributed 3.1 to 3.6%. The osmotic contribution of Na+ increased f rom 0.1-2.1% for nontreated plants to 8.6-15.5% and 15.6-20.0% for the 100 mM and 200 mM salt-treated plants, respectively. The mannitol con tribution to Psi pi(FT) reached a maximum of 9.1% at the end of the sa linization period. We conclude that differences between the two cultiv ars in leaf water relations reflect differences in the exclusion capac ities for Na+ and Cl- ions.