Growth and Development in NaCl-Treated Plants. I. Leaf Na+ and Cl- Concentrations Do Not Determine Gas Exchange of Leaf Blades in Barley

Abstract

Plants of Hordeum vulgare cv. Clipper were grown in gravel culture in solutions containing 0, 100 or 175 mol m-3 NaCl from the seedling stage until anthesis. When salt was first applied, leaf 4 was elongating within the sheath, and leaf 7 had yet to appear on the growing apex. These two leaves were sampled most intensively. Relative to the controls, salinity reduced the final area of all leaves progressively with higher node of insertion, and in the 175 mol m-3 NaCl treatment the reduction was more than twice that in 100 mol m-3 NaCl. Because leaves were at very different stages of development when salt was applied, the progressive reduction inferred there was no evidence of a particular sensitivity to salinity at different stages of leaf expansion. The peak CO2 exchange rate (CER), which occurred shortly after ligule emergence of each leaf was reduced far more in leaf 4 than in higher positions. Indeed, CER averaged throughout the leaf's life, was actually increased by salinity in upper leaves which initiated and expanded during the salt treatment. However, the reduction in leaf area was not offset by this increase in CER. The integration of these adjustments in area per leaf and CER resulted in a reduction in carbon fixation per leaf of about 30 and 60%, by the 100 and 175 mol m-3 treatments respectively for all leaves. There was no obvious relation between CER and Na+ and Cl- concentrations in leaf 7, and between CER and Na+ concentrations in leaf 4. Regression analysis showed that chloride and sodium ions in the leaves accounted for 54% of the statistical variation in CER in leaf 4 but for an insignificant proportion of the variation in leaf 7. As leaf 7 is presumably no different from leaf 4 in its ionic response, we conclude that the high leaf concentrations of Na+ and Cl- did not directly affect the rate of photosynthesis.

Growth and Physiological Responses ofPhaseolusSpecies to Salinity Stress

“…Similar results were found by Rivelli et al [39] for wheat grown at 150 mM NaCl for 30 d. The authors found that the greater effect on RGR occurred within the first 10 d of treatment, after which the difference between treatments largely disappeared. However, in an experiment with barley, the treatment differences in RGR were steady with time, over a 9-week period, RGR averaged 0.13, 0.09 and 0.09 for the 0, 100 and 175 mM NaCl treatments, respectively [40]. At the whole-plant level, decreases observed in RGR could be attributed to a photosynthetic response (ULR) and/or morphological changes (LAR), depending on the species [19].…”

Comparative physiology of salt and water stress

“…Although there can be strong correlations between increases in leaf ion concentrations and reductions in photosynthesis or stomatal conductance, there is as yet no unequivocal evidence for causal relationships. Correlations can disappear when considering different leaves, or different salinities (Rawson et al 1988a). Experiments using different genotypes differing in rates of Na + or Cl -accumulation may be able to distinguish between the effects of salt in the leaf, and salt in the soil.…”

The Use of Hydroponics in Abiotic Stress Tolerance Research

“…Depending on the plant species and aim of the experiment, low, moderate or severe salt stress may be applied. Typically, we add salt twice daily (morning and evening), in 25 mM or 50 mM NaCl www.intechopen.com increments (Shavrukov et al, 2006(Shavrukov et al, , 2009(Shavrukov et al, , 2010a(Shavrukov et al, , 2010b, in agreement with other salinity research groups (Boyer et al, 2008;Dreccer et al, 2004;Forster et al, 1990Forster et al, , 1994Gorham, 1990;Munns & James, 2003;Rawson et al, 1988aRawson et al, , 1988bShah et al, 1987;Watson et al, 2001). We have found that suitable salt stress levels are typically 100-150 mM NaCl for bread wheat (Dreccer et al, 2004;Gorham et al, 1987;Munns & James, 2003;Shah et al, 1987), 150-200 mM NaCl for barley (Forster et al, 1990(Forster et al, , 1994Gorham et al, 1990;Rawson et al, 1988aRawson et al, , 1988bShavrukov et al, 2010a), and 250-300 mM NaCl for tolerant cereals such as wild emmer wheat, Triticum dicoccoides (Shavrukov et al, 2010b), and for saltbush, Atriplex ssp.…”

“…The simplest to use are quartz gravel or river sand, and both are widely used in such systems (Boyer et al, 2008;Dreccer et al, 2004;Greenway, 1962;Munns & James, 2003;Rawson et al, 1988aRawson et al, , 1988b. However, small quartz particles can easily block and damage the pumping system.…”