On the effect of heavy water (D2O) on carbon isotope fractionation in photosynthesis

2008 ◽  
Vol 35 (3) ◽  
pp. 201 ◽  
Author(s):  
Guillaume Tcherkez ◽  
Graham D. Farquhar
Keyword(s):  
Carbon Isotope ◽  
Heavy Water ◽  
Carbon Isotope Discrimination ◽  
Co2 Assimilation ◽  
Xanthium Strumarium ◽  
Phase Component ◽  
Isotope Discrimination ◽  
Internal Conductance ◽  
On Line ◽  
Co2 Addition

Internal conductance to carbon dioxide is a key aspect of leaf photosynthesis although is still not well understood. It is thought that it comprises two components, namely, a gas phase component (diffusion from intercellular spaces to cell walls) and a liquid phase component (dissolution, diffusion in water, hydration equilibrium). Here we use heavy water (D2O), which is known to slow down CO2 hydration by a factor of nearly three. Using 12C/13C stable isotope techniques and Xanthium strumarium L. leaves, we show that the on-line carbon isotope discrimination (Δ13C, or Δobs) associated with photosynthesis is not significantly decreased by heavy water, and that the internal conductance, estimated with relationships involving the deviation of Δ13C, decreased by 8–40% in 21% O2. It is concluded that in typical conditions, the CO2-hydration equilibrium does not exert an effect on CO2 assimilation larger than 9%. The carbon isotope discrimination associated with CO2 addition to ribulose-1,5,bisphosphate by Rubisco is slightly decreased by heavy water. This effect is proposed to originate from the use of solvent-derived proton/deuteron during the last step of the catalytic cycle of the enzyme (hydration/cleavage).

Carbon Isotope Discrimination during C4 Photosynthesis: Insights from Transgenic Plants

1997 ◽  
Vol 24 (4) ◽  
pp. 487 ◽  
Author(s):  
Susanne von Caemmerer ◽  
Martha Ludwig ◽  
Anthony Millgate ◽  
Graham D. Farquhar ◽  
Dean Price ◽  
...  
Keyword(s):  
Carbon Isotope ◽  
Carbon Isotope Discrimination ◽  
Co2 Assimilation ◽  
Small Subunit ◽  
Bundle Sheath ◽  
Cauliflower Mosaic Virus ◽  
35S Promoter ◽  
Coding Region ◽  
Isotope Discrimination ◽  
Flaveria Bidentis

We have measured the discrimination against 13C during CO2 assimilation in Flaveria bidentis wild type plants and in transgenic Flaveria bidentis plants transformed (1) with an antisense RNA construct targeted to the nuclear encoded gene for the small subunit of Rubisco—these plants had reduced amounts of Rubisco, decreased CO2 assimilation rates and increased carbon isotope discrimination, which was also evident in the carbon isotope discrimination of leaf dry matter; and (2) transformed with the mature coding region of carbonic anhydrase, CA, from tobacco (Nicotiana tabacum) in the sense direction under the control of the cauliflower mosaic virus 35S promoter—these plants had slightly increased CA activity in the mesophyll as well as a 2–4-fold increase in CA activity in the bundle-sheath cells. The introduction of tobacco CA manifested itself by a reduction in CO2 assimilation rate and an increase in carbon isotope discrimination. We suggest that the increased carbon isotope discrimination is a result of increased bicarbonate leakage out of the bundle sheath.

Effect of Growth Form, Salinity, Nutrient and Sulfide on Photosynthesis, Carbon Isotope Discrimination and Growth of Red Mangrove (Rhizophora mangle L.)

1992 ◽  
Vol 19 (5) ◽  
pp. 509 ◽  
Author(s):  
GH Lin ◽  
LDSL Sternberg
Keyword(s):  
Stomatal Conductance ◽  
Carbon Isotope ◽  
Carbon Isotope Discrimination ◽  
High Salinity ◽  
Co2 Assimilation ◽  
Transpiration Efficiency ◽  
Growth Forms ◽  
Growth Responses ◽  
Isotope Discrimination ◽  
Red Mangrove

The red mangrove (Rhizophora mangle L.), a dominant mangrove species in Florida, frequently occurs in two distinct growth forms, scrub and tall trees. These two growth forms show significant differences in physiology in the field, with lower CO2 assimilation rate, stomatal conductance, and carbon isotope discrimination or higher transpiration efficiency for the scrub form. To elucidate the possible factors responsible for these physiological differences, we studied the physiological and growth responses of scrub and tall red mangrove seedlings grown hydroponically in the greenhouse under 12 different growth conditions combining three salinities (100, 250, 500 mM NaCl), two nutrient levels (10, 100% strength of full nutrient solution), and two sulfide concentrations (0, 2.0 mM Na2S). The two growth forms showed similar physiological and growth responses to these treatments, suggesting no genetic control of physiological and growth differences between the growth forms of this species. High salinity, low nutrient level, and high sulfide concentration all significantly decreased CO2 assimilation, stomatal conductance, and plant growth, but only salinity significantly decreased intercellular CO2 concentration and leaf carbon isotope discrimination, suggesting that the lower carbon isotope discrimination, or higher transpiration efficiency, observed for scrub mangroves in the field is caused only by high salinity during the dry season. Hypersalinity thus seems to be one of the stressful environmental conditions common to all scrub red mangrove forests studied in southern Florida.

Carbon isotope discrimination during photosynthesis and dark respiration in intact leaves of Nicotiana sylvestris: comparisons between wild type and mitochondrial mutant plants

2001 ◽  
Vol 28 (1) ◽  
pp. 65 ◽  
Author(s):  
Muriel Duranceau ◽  
Jaleh Ghashghaie ◽  
Enrico Brugnoli
Keyword(s):  
Organic Matter ◽  
Carbon Isotope ◽  
Dry Matter ◽  
Carbon Isotope Discrimination ◽  
Dark Respiration ◽  
Nicotiana Sylvestris ◽  
Wild Type ◽  
Isotope Discrimination ◽  
Significant Difference ◽  
On Line

Leaf gas-exchange, carbon isotope discrimination (D) during photosynthesis, carbon isotope composition (d13 C) of leaf dry matter, leaf carbohydrates and ‰ d13 C of dark respiratory CO 2 were measured both in wild type (WT) and in a respiratory mutant of Nicotiana sylvestris Spegazz. plants. The mutation caused a dysfunction of complex I of the respiratory chain which has been described in detail by Gutierres et al. 1997, PNAS, 94, 3436. The aim of this work was to verify if this mutation has an influence on carbon isotope discrimination during photosynthesis and dark respiration. Another objective was to study the possible effect of respiratory fractionation on the isotopic composition of dry matter and on the discrimination measured on-line, in comparison with the expected D based on the model developed by Farquhar et al. 1982, AJPP, 9, 121. On-line D measured on leaves during photosynthesis was lower in the mutants (16.5‰ 0.9) than in the WT (20.1‰ 0.6), mainly due to lower conductance to CO 2 diffusion (both across stomatal pores and in the gaseous and liquid phases across the mesophyll) in the mutants. No statistically significant difference in the fractionation during dark respiration was observed between WT and mutant plants. However, respiratory CO 2 was enriched in 13 C compared to sucrose and glucose by about 2–3 and 2.5–4‰, respectively. The enrichment in 13 C (about 2‰) observed in leaf metabolites and leaf organic matter in the mutants compared to the WT can be explained by differences in .during photosynthesis. However, the fractionation in the whole-leaf organic matter of both WT and mutant plants was higher (more depleted in 13C) than expected based on the .values obtained with on-line measurements during photosynthesis. The observed discrimination during dark respiration, releasing 13 C-enriched CO 2 , may partly explain the higher fractionation in the remaining leaf organic matter compared to the overall discrimination during photosynthesis, as measured on-line.

scholarly journals To concentrate or ventilate? Carbon acquisition, isotope discrimination and physiological ecology of early land plant life forms

2008 ◽  
Vol 363 (1504) ◽  
pp. 2767-2778 ◽  
Author(s):  
Moritz Meyer ◽  
Ulli Seibt ◽  
Howard Griffiths
Keyword(s):  
Carbon Isotope ◽  
Life Form ◽  
Carbon Isotope Discrimination ◽  
Physiological Ecology ◽  
Life Forms ◽  
Land Plant ◽  
Tissue Water ◽  
Isotope Discrimination ◽  
Plant Life Forms ◽  
Internal Conductance

A comparative study has been made of the photosynthetic physiological ecology and carbon isotope discrimination characteristics for modern-day bryophytes and closely related algal groups. Firstly, the extent of bryophyte distribution and diversification as compared with more advanced land plant groups is considered. Secondly, measurements of instantaneous carbon isotope discrimination ( Δ ), photosynthetic CO 2 assimilation and electron transport rates were compared during the drying cycles. The extent of surface diffusion limitation (when wetted), internal conductance and water use efficiency (WUE) at optimal tissue water content (TWC) were derived for liverworts and a hornwort from contrasting habitats and with differing degrees of thallus ventilation (as intra-thalline cavities and internal airspaces). We also explore how the operation of a biophysical carbon-concentrating mechanism (CCM) tempers isotope discrimination characteristics in two other hornworts, as well as the green algae Coleochaete orbicularis and Chlamydomonas reinhardtii . The magnitude of Δ was compared for each life form over a drying curve and used to derive the surface liquid-phase conductance (when wetted) and internal conductance (at optimal TWC). The magnitude of external and internal conductances, and WUE, was higher for ventilated, compared with non-ventilated, liverworts and hornworts, but the values were similar within each group, suggesting that both factors have been optimized for each life form. For the hornworts, leakiness of the CCM was highest for Megaceros vincentianus and C. orbicularis (approx. 30%) and, at 5%, lowest in C. reinhardtii grown under ambient CO 2 concentrations. Finally, evidence for the operation of a CCM in algae and hornworts is considered in terms of the probable role of the chloroplast pyrenoid, as the origins, structure and function of this enigmatic organelle are explored during the evolution of land plants.

Carbon isotope discrimination in leaf and stem sugars, water-use efficiency and mesophyll conductance during different developmental stages in rice subjected to drought

1998 ◽  
Vol 25 (4) ◽  
pp. 489 ◽  
Author(s):  
A. Scartazza ◽  
M. Lauteri ◽  
M.C. Guido ◽  
E. Brugnoli
Keyword(s):  
Water Use Efficiency ◽  
Carbon Isotope ◽  
Water Use ◽  
Carbon Isotope Discrimination ◽  
Developmental Stages ◽  
Grain Filling ◽  
Co2 Assimilation ◽  
Mesophyll Conductance ◽  
Isotope Discrimination ◽  
Use Efficiency

Carbon isotope discrimination (Δ), growth analysis, water-use efficiency (WUE) and gas exchange characteristics were studied in rice plants (Oryza sativa L.) subjected to drought during different developmental stages. Drought caused major effects on growth, WUE, Δ and photosynthetic CO2 assimilation. Substantial differences in the Δ of the bulk biomass among different organs and in carbohydrates extracted from leaves and stems were observed. Possible influences of chemical composition, fractionation during translocation and seasonal changes in the ratio of intercellular and atmospheric partial pressures of CO2 on such differences in Δ are discussed. Stem carbohydrate Δ was correlated with relative growth rate, and, during early grain filling, was negatively correlated with WUE measured between flowering and early grain filling. Δ in leaf sugars was used to estimate mesophyll conductance (gm), the conductance to CO2 diffusion inside leaves, from the intercellular air spaces to the chloroplast. During ontogeny, gm showed a marked progressive decrease, evident in both droughted plants and fully irrigated controls. There was a positive correlation between the rate of CO2 assimilation and gm. The analysis of Δ in leaf and stem carbohydrates is proposed as a useful indicator of growth, WUE and photosynthetic parameters relevant for yield of rice under drought-prone conditions.

Determination of the Average Partial Pressure of CO2 in Chloroplasts From Leaves of Several C3 Plants

1991 ◽  
Vol 18 (3) ◽  
pp. 287 ◽  
Author(s):  
SV Caemmerer ◽  
JR Evans
Keyword(s):  
Partial Pressure ◽  
Carbon Isotope ◽  
Carbon Isotope Discrimination ◽  
Isotope Composition ◽  
Co2 Assimilation ◽  
Carbon Isotope Composition ◽  
C3 Plants ◽  
Isotope Discrimination ◽  
Partial Pressure Of Co2 ◽  
Transfer Conductance

Measurements of CO2 and water vapour exchange by leaves were combined with measurements of carbon isotope composition (13C/12C) of CO2 in the air passing over the leaf. Carbon isotope discrimination during CO2 uptake was determined from the difference in carbon isotope composition of the air leaving the leaf chamber with or without a leaf enclosed. Leaves of wheat plants grown with different nitrogen nutrition and leaves of several other species were examined. The measurements, made at different irradiances for a given leaf, showed that carbon isotope discrimination was strongly correlated with the rate of CO2 assimilation as well as the ratio of intercellular to ambient partial pressure of CO2, pI/pa. A function relating carbon isotope discrimination to the rate of CO2 assimilation was used to estimate the CO2 transfer conductance, gw, from the substomatal cavities to the sites of carboxylation for individual leaves. The photosynthetic capacity correlated with the CO2 transfer conductance, gw, and the average ratio of chloroplastic to intercellular partial pressure of CO2, pI/pa, was 0.7. This means that in general under high irradiance, the ratio of chloroplastic to ambient partial pressure of CO2 is about 0.5. In wheat, variation in gw was correlated with the chloroplast surface area appressing intercellular airspaces.

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