Eco-physiological studies on Indian arid zone plants : V. A. Screening of some species for the C4-pathway of photosynthetic CO2-fixation.

Plants of the Indian desert belonging to 29 families, 85 genera and 105 species of angiosperms were screened for the possible occurrence of the C4-pathway of photosynthetic CO2-fixation. The criteria used for screening were leaf anatomy and/or δ13C values. The results indicated the occurrence of the C4-pathway in members of 3 new families (Acanthaceae, Cleomaceae, Scrophulariaceae), 10 new genera (Aerva, Anticharis, Blepharis, Elyonurus, Glossocardia 1 , Gynandropsis, Melanocenchris, Sehima, Sesuvium, Zalaeya) and 34 new species of the angiosperms. All the grasses investigated were found to possess the C4-pathway. Cuscuta hyalina, a phloem-parasite, growing on C4 hosts (Tribulus, Zalaeya) also revealed δ13C value very close to that found in the host plants.