The photosynthetic pathway types of some desert plants from India, Saudi Arabia, Egypt, and Iraq

Plants collected from different habitats in the deserts of India, Saudi Arabia, Egypt, and Iraq were screened for their photosynthetic CO₂-fixation pathways using δ¹³C and δD values. The analyses comprised 128 species belonging to 108 genera and 46 families. Neither the C₄ nor the CAM pathway was prevalent in the plant families analyzed except in Poaceae, where C₄ metabolism absolutely dominated. Of 93 dicotyledonous plants, only 10 exhibited a C₄ pathway and only 2 were CAM plants. The study shows that some species reported by other workers as C₄ plants are clearly C₃ ones.