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Ionic relations of Phillyrea latifolia L. plants during NaCl stress and relief from stress
No full textTwo experiments were conducted on Phillyrea latifolia L. plants exposed to increasing NaCl concentrations at the root zone in hydroponic culture. Growth, ion fluxes within the plant, and rates of excretion by glandular trichomes were measured during both salinity stress and relief periods. The reduction in relative growth rate (RGR) of plants treated with 100 and 200 mM external NaCl was more marked when RGR was calculated on a fresh weight (FW) basis than on a dry weight (DW) basis. The RGR of previously salt-treated plants, expressed on a FW basis, did not differ from that of the controls over 5 weeks of relief from stress, whereas RGR calculated on a DW basis did not fully recover. Fluxes of Na+ and K+ appeared highly regulated. Sodium transport to the leaf of 100 mM salt-treated plants equalled that of the controls, whereas Na+ transport to the leaf was higher in 200 mM salt-treated plants. Selectivity ratio for K+ and Na+ transport to the leaf was increased by salt treatments. The exclusion ability for Cl- was markedly lower than that for Na+ at 300 and 400 mM external NaCl. The excretion of Na+ and Cl- by glandular trichomes was very low at all external NaCl concentrations and substantially higher in basal leaves than in apical leaves. These results indicate that in P. latifolia, mechanisms of salt tolerance operate by excluding sodium and maintaining high selectivity for uptake and transport of K+, whereas the excretion of toxic ions is of minor significance
Antioxidant defenses in plants: A dated topic of current interest
No full text: Plants have been challenged against oxidative stress since their appearance on land [...]
Ionic relations and osmotic adjustment in olive plants under salinity stress
No full textSelf-rooted olive plants (cvs. Frantoio and Leccino) were exposed to 0, 100 and 200 mM NaC1 in hydroponic culture for 5 weeks. Growth, leaf water relations, cations and soluble carbohydrates content were measured. The two cultivars, differing in leaf salt accumulation, were not significantly different for Na uptake, whereas Na transport rate was lower in the salt-tolerant cv. Frantoio. Ions largely contributed to the salinity-induced changes in leaf osmotic potential, which decreased earlier in the salt-sensitive cv. Leccino than in the salt-tolerant cv. Frantoio. The contribution of soluble carbohydrates, namely glucose and mannitol, was less important than that of cations
The effect of some exogenous growth regulators on rhizogenesis in Olea europaea L. cuttings.
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Analysis of leaf water relations of two olive (Olea europaea) cultivars differing in tolerance to salinity
No full textOne-year-old rooted cuttings of olive (Olea europaea L. cvs. Frantoio and Leccino) were grown either hydroponically or in soil in a greenhouse. 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 determine whether previously demonstrated genotypic differences in tolerance to salinity were related to water relations parameters. Exposure to high salt concentrations resulted in reductions in predawn water potential (Ψ(w)), osmotic potential at full turgor (Ψ(πFT)), osmotic potential at turgor loss point (Ψ(πTLP)), and relative water content (RWC) in both cultivars, regardless of the growth substrate. Leaf Ψ(w) and RWC returned to values similar to those of controls by the end of the relief period. The effect of salinity on Ψ(π appeared earlier in Leccino than in Frantoio. Values fur Ψ(πFT) were -2.50, -2.87, and -3.16 MPa for the 0, 100, and 200 mM salt-treated Frantoio plants, respectively, and -2.23, -2.87, and -3.37 MPa for the corresponding Leccino plants. Recovery of Ψ(π) 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 (Ψ(p)) compared to control plants. Net solute accumulation was higher in Leccino, the salt-sensitive cultivar, than in Frantoio. In controls of both cultivars, cations contributed 39,9 to 42.0% of the total Ψ(π(FT), mannitol and glucose contributed 27.1 to 30.8%, and other soluble carbohydrates contributed 3.1 to 3.6%. The osmotic contribution of Na+ increased from 0.1-2.1% for non-treated plants to 8.6-15.5% and 15.6- 20.0% for the 100 mM and 200 mM salt-treated plants, respectively. The mannitol contribution to Ψ(πFT) reached a maximum of 9.1% at the end of the salinization period. We conclude that differences between the two cultivars in leaf water relations reflect differences in the exclusion capacities for Na+ and Cl- ions
Gas exchange, water relations and osmotic adjustement in two scion/rootstock combinations of Prunus under various salinity concentrations
No full textGrowth, gas exchange and water relations have been studied on hydroponically grown peach (cv. Armking) plants, grafted on GF677 (Arm/GF) and Mr.S.2/5 (Arm/MrS), exposed to 0, 40, 80 and 120 mM NaCl concentration, over a four-week period. Plant performance was also evaluated during a subsequent four-week period of relief from stress, by supplying the plants with a complete nutrient solution. Salinity stress reduced growth and net assimilation rate to a greater extent in Arm/GF than in Arm/MrS plants. Salt-induced water stress was more severe in Arm/GF than Arm/MrS leaves, and particularly during the first two weeks of treatment. On the other hand, leaf osmotic potential at full turgor (ψπFT) of salt-treated Arm/MrS received a markedly greater contribution from Na+ and Cl - than salt-treated Arm/GF plants. By contrast, divalent cations and K+ made a substantially greater contribution to leaf ψπFT of salt-treated Arm/GF than to the corresponding ψπFT of Arm/MrS plants. Salinity stress markedly altered leaf carbohydrate composition and led to a preferential accumulation of sorbitol, independent on the scion/rootstock combination. Salt-treated Arm/GF but not Arm/MrS plants stored most of the Na+ and Cl- loaded in the shoot, into basal (old) leaves. The rootstock ability to control the accumulation of salt in the scion leaves during the salinity stress, determined striking differences in the recovery of photosynthetic performances, during the relief period. A full recovery of A and gs was detected in both 40 and 80 mM salt-treated Arm/GF leaves, but only in 40 mM salt-treated Arm/MrS, at the end of the relief treatment. These data indicate a greater efficiency of GF677 than Mr.S.2/5 in protecting peach plants from the deleterious effects of NaCl stress
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