Carbon isotope discrimination by Sorghum bicolor under CO₂ enrichment and drought

Abstract

Summary• Sorghum bicolor was exposed to free-air CO 2 enrichment (FACE) and drought at the Maricopa Agricultural Center, AZ, USA, in summer 1998. We predicted that bundle sheath leakiness ( Φ ) would be insensitive to FACE under well-irrigated (wet) conditions, but would be lower in FACE compared with control-CO 2 treatments when irrigation was withheld (dry).• Leaf and air δ 13 C values and leaf p i / p a from gas exchange were measured to estimate carbon isotope discrimination ( ∆ ) and Φ . Midday leaf water potential ( Ψ ) and photosynthetic rate were simultaneously measured to evaluate the influence of plant water status on Φ and the association between Φ and carbon gain.• Irrigation treatments affected Ψ , p i / p a , ∆ and Φ in control CO 2 and FACE rings. Differences in leaf ∆ between wet-and dry-treatment plots resulted from changes in Φ and to stomatal influences on p i / p a . FACE had very little effect on Ψ , ∆ and Φ in wet-treatment plots. However, Φ and ∆ in dry plots were higher in control than in FACE rings.• FACE ameliorated the effects of drought on bundle sheath leakiness and ∆ by reducing transpiration, prolonging soil water availability and enhancing plant water status. Direct effects of CO 2 enrichment on C 4 photosynthetic metabolism in Sorghum apparently are minimal and indirect effects depend on soil water supply.

Carbonic Anhydrase and Its Influence on Carbon Isotope Discrimination during C4 Photosynthesis. Insights from Antisense RNA in Flaveria bidentis

“…Growth conditions (e.g. elevated CO 2 and water stress) have also been reported to influence the balance of the C 4 and C 3 cycles, leading to an altered isotopic composition of dry matter (Watling et al, 2000;Williams et al, 2001), although the influence on CA was not addressed in these studies.…”

Global Photosynthesis and its Regulatory Role in Natural Carbon Cycle

“…Among them the variations of CO 2 concentration in the environment exerts the strongest effect. High CO 2 concentrations results in 12 C enrichment of biomass in the in vitro experiments [11,20,23]. Similarly pH manifests itself in aquatic environment.…”

“…Later the role of carbon isotope effect of photorespiration was recognized as important [22,28] and some researchers have indicated the role of oxygen concentration on photorespiratory function of Rubisco [23,29]. It was shown that low O 2 content caused the observed enrichment of organic matter 12 C [30].…”

Stable Carbon Isotope Discrimination Is under Genetic Control in the C4 Species Maize with Several Genomic Regions Influencing Trait Expression

“…C is at least in part associated with p i p a 21 (Madhavan et al, 1991;Henderson et al, 1992Henderson et al, , 1998Williams et al, 2001). As this association is not as strong as in C 3 species, the involvement of additional processes is very likely.…”