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).
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