Photosynthetic pathways, distribution, and ecological characteristics of grass species in egypt.

This study is based both on our own results, especially δ13C analyses, and on data in the literature. Of the 225 species of Poaceae reported from Egypt, 105 species show the C3 and 120 the C4 type of photosynthetic CO2 fixation. Winter annual and perennial grasses active in winter are mainly C3 species, while summer annuals and the other perennials are mainly C4 species. The percentage of C3 species decreases with decreasing latitude. This seems to be mainly related to increasing temperatures. The C3 grass species are found preferentially in the Mediterranean, Irano-Turanian, Mediterranean/Irano-Turanian, and Saharo-Arabian chorotypes, while the C4 species are mainly found in the Sudanian, Saharo-Arabian/Sudanian and Tropical chorotypes. In Egypt, the NADP+-ME and NAD+-ME subtypes of C4 photosynthesis are found in about equal numbers of C4 species, while the PCK subtype is relatively rare

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