Compared effects of sudden and progressive impositions of salt stress in three durum wheat (Triticum durum Desf.) cultivars

The effect of sudden vs. progressive exposure to salt stress at the seedling stage was investigated in three durum wheat cultivars differing in their mean level of sale and drought resistance. Both procedures of stress imposition induced a decrease in relative growth rates, K concentrations and leaf osmotic potential values, as well as an increase in Na, proline and soluble sugar contents. Growth inhibition was largest in the drought-resistant cultivar Omrabi 5, suggesting that drought and salt-resistance are not necessarily linked in Triticum durum. Suddenly-applied NaCl often appeared more detrimental than progressive exposure. Quantitative differences between the effects of the two modes of stress imposition suggested the existence of a precocious adaptative mechanism in response to progressive exposure but varied according to the physiological parameter used to evaluate plant behaviour, the final dose of NaCl and the genotype. The most salt-resistant cultivar (Belikh) was the less influenced by the kinetics of stress application. The modification of the mineral nutrition- and osmotic adjustment-related parameters is discussed in relation to the specific physiological strategy of salinity resistance postulated in Triticum durum and in light of the contrasting evidence in the literature.