Photosynthetic compounds (14C) and malate under shock salt stress impact of different plants in the western desert of Egypt

Many plant species in the Egyptian north-western desert provide numerous benefits as providing sources of food, fuel-wood, and traditional medicine. We induced photosynthesis using 14C to predict the photosynthetic pathway employed by the plants under shock stress. Results indicated that the shock stress greatly inhibits photosynthetic rates of Ononis vaginalis and Zygophyllum album while affecting others (Gymnocarpos decandrum and Plantago albicans) to a lesser extent. A large amount of 14C was incorporated in total amino acids and sucrose during photosynthesis. The increase in the content of labeled organic acids in Z. album under stress, the accumulation of night malate, and the presence of Kranz layer indicated a change in the photosynthetic pathway from C4 to CAM. The palatable species (Plantago albicans) characterized by highest content of amino acids and sugar phosphate as compared with the other studied species. Studying plant metabolism under desert conditions is important to understand the strategies for salt-shock tolerance in these species.