C4 plants in the deserts of China: occurrence of C4 photosynthesis and its morphological functional types

C₄ photosynthetic pathway and morphological functional types were determined for 104 species in 45 genera and 10 families from the deserts of China. 67 C₄ species (64.4 %) were found in Dicotyledoneae (e.g. Chenopodiaceae, Polygonaceae, and Amaranthaceae), the other 37 species were in Monocotyledoneae (e.g. Gramineae, Cyperaceae, and Commelinaceae). 36.5 % of the Chenopodiaceae species (predominantly members of the genera Anabasis, Atriplex, Kochia, Salsola, and Suaeda) identified in the desert regions were found with C₄ photosynthesis, which was about 48 % of the total C₄ species. Many C₄ species (58.7 %) were annuals (e.g. Amaranthus, Atriplex, Digitaria, Eragrostis, Kochia, and Salsola) and experienced long-term droughts, high temperature, and high irradiance. Relatively more shrub C₄ species (28 species of 104) were found in Chenopodiaceae (e.g. Anabasis, Camphorosma, Haloxylon, and Salsola) and Polygonaceae (e.g. Calligonum) in the desert regions. Most of shrub C₄ species with small leaf area were no more than 1 m in height and distributed in sandy soils. Composition of relatively more annual species, shrubs, and Chenopodiaceae C₄ species was the primary characteristic for the C₄ species occurrence in deserts, and this was remarkably related with the arid environmental conditions.