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 seedlin g stage was investigated in three durum wheat cultivars differing in their mean level of sale and drought resistance. Both procedures of stress imposi tion induced a decrease in relative growth rates, K concentrations and leaf osmotic potential values, as well as an increase in Na, proline and solubl e sugar contents. Growth inhibition was largest in the drought-resistant cu ltivar Omrabi 5, suggesting that drought and salt-resistance are not necess arily linked in Triticum durum. Suddenly-applied NaCl often appeared more d etrimental 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 var ied according to the physiological parameter used to evaluate plant behavio ur, the final dose of NaCl and the genotype. The most salt-resistant cultiv ar (Belikh) was the less influenced by the kinetics of stress application. The modification of the mineral nutrition- and osmotic adjustment-related p arameters is discussed in relation to the specific physiological strategy o f salinity resistance postulated in Triticum durum and in light of the cont rasting evidence in the literature.