Abstract
To evaluate durum wheat (Triticum durum Desf.) tolerance to osmotic stress at the water potential levels induced by polyethylene glycol 6000 and NaCl solutions at an early stage of plant growth. Each, on germination and early seedling stages, were investigated for two durum wheat genotypes differing in drought tolerance (boefi and leucurum) at laboratory, in Iran in 2010. This investigation was performed as factorial experiment under complete randomized design with four replications. Daily and final germination as well as germination and seedling emergence rate, and seedling fresh and dry weight were measured in the study under controlled conditions. Results showed those germination rate was delayed by both solutions in both varieties, with differences between genotypes among growth stages, given that boefi genotype showed a higher germination rate than leucurum genotype in NaCl. NaCl had a lesser effect on genotypes in terms of germination rate and the final germination than did polyethylene glycol (PEG). This conclusively proves that the adverse effect of PEG on germination and early seedling growth was due to the osmotic effect rather than the specific ion. Seedling growth was reduced by both stresses. But NaCl usually caused less damage than PEG to durum wheat seedlings, suggesting that NaCl and PEG acted through different mechanisms. This difference in cultivar’s behavior according to the growth conditions is discussed. It was concluded that inhibition in germination at equivalent water potential levels of NaCl and PEG was mainly due to an osmotic effect rather than did salt toxicity. Finally boefi genotype showed that resistance to both NaCl and PEG stress than leucurum genotype. Keywords: Durum wheat, germination, NaCl, polyethylene glycol (PEG).
Highlights
For thousands of years, durum wheat (Triticum turgidum, L.var.Durum Defs) has been cultivated both irrigated and rain-fed in the west of Iran
This conclusively proves that the adverse effect of polyethylene glycol (PEG) on germination and early seedling growth was due to the osmotic effect rather than the specific ion
Germination and early seedling growth (10 days) of these genotypes were studied in two experiments using distilled water and osmotic potentials (-0.2, -0.4, -0.6 and -0.8 MPa), which were prepared by adding NaCl or PEG-6000 to distilled water according to Van’t Hoff’s equation (Lang, 1967) to have the same osmotic potential in both NaCl and PEG-6000 solutions
Summary
Durum wheat (Triticum turgidum, L.var.Durum Defs) has been cultivated both irrigated and rain-fed in the west of Iran. High concentrations of salts in the soil solution impair cell metabolism and photosynthesis but impose an osmotic stress on cell water relations by increasing the toxicity of sodium in the cytosol (sayar et al, 2010). The germination of seeds is affected by creating an external osmotic potential that prevents water uptake due to the toxic effects of Na+ and Cl- ions both during imbibition and seedling establishment (Murillo-Amador et al, 2002). In Tunisia, durum wheat is commonly grown on marginal soils under rainfed (natural and nonirrigated) conditions It suffers often from drought and salt stresses. The study presented here deals with the response of two cultivars of wheat to NaCl and water stress at germination and early seedling growth stage
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