conditions and awaken interest in the importance of local C 4 crops, the conservation of threatened C 4 taxa, and awareness of human impacts on the rapid environmental changes in the region. Keywords: C 3-C 4 switching plants, C 4 crops, Chenopodiaceae, conservation, Irano-Turanian region, Poaceae, single-cell C 4 , d 13 C-isotope ratio the Pamir (Pyankov et al., 2000a). In tropical and subtropical Asia, Africa, Australia, and South America the majority of C 4 Poaceae confirm the trend observed in Europe, being mainly distributed in hot climates with the obligatory presence of