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Does Bienertia cycloptera with the single-cell system of C₄ photosynthesis exhibit a seasonal pattern of δ¹³C values in nature similar to co-existing C₄ Chenopodiaceae having the dual-cell (Kranz) system?

Akhani, Hossein, Lara, María Valeria, Ghasemkhani, Maryam, Ziegler, Hubert, Edwards, Gerald E.
Photosynthesis research 2009 v.99 no.1 pp. 23-36
Bienertia, C3 plants, C4 photosynthesis, C4 plants, Suaeda, annuals, bracts, carbon, cotyledons, growing season, habitats, isotopes, leaves, seeds, shoots, Iran
Family Chenopodiaceae is an intriguing lineage, having the largest number of C₄ species among dicots, including a number of anatomical variants of Kranz anatomy and three single-cell C₄ functioning species. In some previous studies, during the culture of Bienertia cycloptera Bunge ex Boiss., carbon isotope values (δ¹³C values) of leaves deviated from C₄ to C₃-C₄ intermediate type, raising questions as to its mode of photosynthesis during growth in natural environments. This species usually co-occurs with several Kranz type C₄ annuals. The development of B. cycloptera morphologically and δ¹³C values derived from plant samples (cotyledons, leaves, bracts, shoots) were analyzed over a complete growing season in a salt flat in north central Iran, along with eight Kranz type C₄ species and one C₃ species. For a number of species, plants were greenhouse-grown from seeds collected from the site, in order to examine leaf anatomy and C₄ biochemical subtype. Among the nine C₄ species, the cotyledons of B. cycloptera, and of the Suaeda spp. have the same respective forms of C₄ anatomy occurring in leaves, while cotyledons of members of tribe Caroxyloneae lack Kranz anatomy, which is reflected in the δ¹³C values found in plants grown in the natural habitat. The nine C₄ species had average seasonal δ¹³C values of -13.9[per thousand] (with a range between species from -11.3 to -15.9[per thousand]). The measurements of δ¹³C values over a complete growing season show that B. cycloptera performs C₄ photosynthesis during its life cycle in nature, similar to Kranz type species, with a seasonal average δ¹³C value of -15.2[per thousand].