Carbon, Hydrogen, and Oxygen Isotope Ratios of Cellulose from Plants Having Intermediary Photosynthetic Modes

Abstract

Carbon and hydrogen isotope ratios of cellulose nitrate and oxygen isotope ratios of cellulose from species of greenhouse plants having different photosynthetic modes were determined. When hydrogen isotope ratios are plotted against carbon isotope ratios, four clusters of points are discernible, each representing different photosynthetic modes: C3 plants, C4 plants, CAM plants, and C3 plants that can shift to CAM or show the phenomenon referred to as CAM-cycling. The combination of oxygen and carbon isotope ratios does not distinguish among the different photosynthetic modes. Analysis of the carbon and hydrogen isotope ratios of cellulose nitrate should prove useful for screening different photosynthetic modes in field specimens that grew near one another. This method will be particularly useful for detection of plants which show CAMcycling.There are three major photosynthetic pathways in plants: C3,2 C4, and CAM. Carbohydrates in all three are synthesized by the Calvin cycle. In C3 plants, CO2 is fixed directly into the Calvin cycle, with the primary carboxylation product being a threecarbon compound (11). In C4 and CAM plants, the initial carboxylation product is a four-carbon compound (10,

Crassulacean Acid Metabolism in the Gesneriaceae

“…This pattern of gas exchange is typical of CAM-cycling species (Sipes and Ting, 1985). CAM-cycling of C. crassifolia is further supported by the carbon and deuterium isotope composition values of -24.6%co and + 12.0%co, respectively (as reported by Ting et al, 1985), and these isotope composition values are comparable to other CAM-cycling species (Sternberg et al, 1984).…”

Crassulacean Acid Metabolism in the Gesneriaceae

“…The CAM pathway of photosynthesis occurs in tropical epiphytes of the Bromeliaceae (McWilliams, 1970;Medina and Troughton, 1974), Orchidaceae (Knauft and Arditti, 1969;McWilliams, 1970;Neales and Hew, 1975;Sinclair, 1984), Cactaceae (Wiehler, 1982), Rubiaceae (Winter et al, 1983), and the Piperaceae (Sternberg, Deniro and Ting 1984;Sipes and Ting, 1985). CAM is also found in some epiphytic ferns of the Polypodiaceae (Wong and Hew, 1976).…”

Compensation Point and Isotopic Characteristics of C3/C4 Intermediates and Hybrids in Panicum

“…In addition to the well known separation of C3 plants from C4 and CAM plants based on stable carbon isotope ratios (17), oxygen and hydrogen isotope ratios ofcellulose and cellulose nitrate, respectively, also are influenced by photosynthetic mode (20,(22)(23)(24)(25). Analysis of C3, C4, and CAM plants growing in the vicinity of each other show that cellulose nitrate from CAM plants is enriched in deuterium relative to C3 and C4 plants (20, 22, 25).…”

“…These plants exhibit several physiological, anatomical, or biochemical characteristics of two different photosynthetic modes. For example, several species of Peperomia as well as species in Codananthe, Pereskia, Cissus, and Sedum have characteristics both of CAM and C3 plants and are called CAM-cyclers (15,16,19,(24)(25)(26)(27). Species in the Portulaca genus have physiological/biochemical characteristics of C4 photosynthesis and Kranz anatomy, as well as succulence and acid flux typical of CAM plants (13,14).…”

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ABSTRACT 16,19,[24][25][26][27]Isotope analysis of plant matter provides a powerful method of studying photosynthetic modes. In addition to the well known separation of C3 plants from C4 and CAM plants based on stable carbon isotope ratios (17), oxygen and hydrogen isotope ratios ofcellulose and cellulose nitrate, respectively, also are influenced by photosynthetic mode (20,(22)(23)(24)(25).

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