Water is a limiting factor for plant production and water scarcity has a significant effect on reducing plant growth, photosynthesis, and crop yield. During the last year, Moroccan growers suffered from the water scarcity caused by global warming. Area of vegetable production was reduced during the last years. Saving irrigation water is currently one of the main goals of the growers for the yield optimization in such conditions. The present work aims to evaluate the impacts of different irrigation regimes on photosynthesis (chlorophyll a fluorescence), stress index, plant growth and biomass and yield of lettuce (Lactuca sativa) grown under the semi-arid and Mediterranean conditions of the northeast of Morocco. The experiments were conducted in an open-field commercial farm of lettuce (var. Romain), located in Nador province. Three irrigation regimes were used as a treatment: (i): grower irrigation (Control); (ii) cutting 25% (Tr-75%) and (iii) cutting 50% (Tr-50%) of the grower irrigation amount. Split plot was used for the experimental design. A Digital soil moisture sensor was used in this experiment. Measurements of plant growth were measured each 2 weeks and the plant yield, fresh and dry weight of roots and leaves were recorded at the end of the experiment. Physiological parameters such as leaf relative water content (RWC) and leaf chlorophyll fluorescence were taken. Results showed significant differences for plant growth, yield, leaves, and roots fresh and dry weight. The chlorophyll fluorescence data showed different performance of plant stress under the three irrigation regimes.