Physiological changes after exposure to and recovery from polyethylene glycol-induced water deficit in roots and leaves of durum wheat (Triticum durum Desf.) cultivars differing in drought resistance

The effects of water stress on the behaviour of hydroponically-grown seedli ngs of 3 durum wheat ( Triticum durum Desf.) cvs. differing in drought resi stance (Kabir 1, drought sensitive; Omrabi 5 and Haurani, drought resistant ) were investigated under controlled environmental conditions. Fresh weight (FW), water content (WC), osmotic potential (Psi(s)), organic and inorgani c solute concentrations in roots and shoots were measured after 7 days of e xposure to polyethylene glycol (PEG at 0, 10 or 20 %) and after 2 and 7 day s of recovery following stress relief. Water stress decreased FW WC and Psi s, and increased root to shoot ratio (R/S) and soluble sugar, proline and other amino acid concentrations in both roots and leaves of all cvs. Water stress effect on inorganic solutes was different depending on the ion natur e and on the plant part. Most of the significant changes were recorded in r esponse to 20 % PEG. Roots and shoots roughly reacted in the same way to wa ter stress but differed in terms of the intensity and rapidity of the respo nses. After stress relief, almost all parameters returned to control level; however, for some of them, roots and shoots differed in the rapidity of th eir recovery. Growth parameters as well as organic solute accumulation reve aled differences in the behaviour of the 3 different cvs. when confronted t o water stress. Our results demonstrated the high plasticity of durum wheat at the vegetative stage and suggest that the maintenance of higher root gr owth and osmotic adjustment in water stress conditions could confer an impr oved resistance of this species to drought.