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Membrane lipids, peroxidation, P-carotene content, proline accumulation, and photosynthetic activity were analyzed in two Moroccan wheat (Triticum aestivum L.) varieties, Nasma (adapted to irrigated zone) and Tigre (adapted to semi-arid zone). Plants were grown in plastic pots under laboratory irrigation and water stress conditions. One set of plants was subjected to regular water irrigation and another to water stress conditions created by water deprivation. After 30 days of water shortage (corresponding to 8% of field capacity), the leaves’ fatty acid contents, especially that of Octadecatrienoic acid (18:3 Delta(9,12,15)), i.e. the major unsaturated fatty acid, significantly decreased. The decrease was more pronounced in Nasma varieties than in Tigre. The amount of galactolipids, phospholipids, and P-carotene decreased in droughted plants of both local wheat varieties while the content of neutral lipids increased. Lipid peroxidation, assessed as the content of malondialdehyde (MDA), was found to be augmented under stress. (The rate of increase was 41% and 19% in Nasma and Tigre respectively). The amount of proline accumulated in leaf segments of both varieties subjected in vitro to osmotic stress was suppressed by addition of octadecanoic or octadecadienoic acids. The inhibition of photosynthetic capacity under osmotic stress was reduced when fatty acids were added in medium. A positive relationship was observed between proline accumulation and membrane stability. The mechanisms of these physiological responses to water stress are discussed.