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.

Broad sense heritability and genotype × environment interaction for carbon isotope discrimination in field-grown wheat

1992 ◽  
Vol 43 (5) ◽  
pp. 921 ◽  
Author(s):  
AG Condon ◽  
RA Richards
Keyword(s):  
Carbon Isotope ◽  
Dry Matter ◽  
Carbon Isotope Discrimination ◽  
Genotypic Variation ◽  
Broad Sense ◽  
Environment Interaction ◽  
Broad Sense Heritability ◽  
Isotope Discrimination ◽  
Average Value ◽  
Plant Parts

Carbon isotope discrimination (-) has been proposed as a possible selection criterion for greater water use efficiency in breeding programs for water-limited environments because it provides an integrative assessment of genotypic variation in leaf transpiration efficiency. Considerable genotypic variation for - has been demonstrated in wheat, but environmental factors may cause even larger changes in the value of - measured in plant dry matter, which could compromise the effective use of - in breeding programs. In this study we assess broad-sense heritability of - and the significance of genotype x environment interaction for - in field-grown wheat. Another objective was to identify the most effective growth stage or plant part to characterize genotypic variation in -. Experiments were done using several large sets of genotypes (between 8 and 40, usually c. 20) grown in a range of field environments spanning the southern Australian wheat-belt. Carbon isotope discrimination was determined on unreplicated grain samples from seven Interstate Wheat Variety trials grown in 1983 and 1984 and on several plant parts taken from replicated experiments conducted at four locations in south-west New South Wales from 1985 to 1988. From these replicated experiments broad-sense heritabilities for - were calculated on a genotype mean basis h2-M) and on a single-plot basis (h2-P). In dry matter sampled from several environments, site-mean - ranged from 21.0 x 10-3 to 18.9 x 10-3 for early-formed dry matter and from 16.4 x 10-3 to 13.4 x 10-3 for grain. When followed in a single environment, the value of - fell from c. 20 x 10-3 in early-formed leaves to 15.4 x 10-3 in the grain. Variation among genotypes in - of different plant parts was always significant, and was typically c. 2 x 10-3 . Among Australian wheats, low values of - (implying greater transpiration efficiency) were strongly associated with the WW15 genetic background. Estimates of broad-sense heritability for - averaged over 95%, on a genotype mean basis, in experiments where common genotypes were grown in numerous environments. In individual trials, heritability was lowest for plant material sampled near anthesis (average value for h2-M, 83% and for h2-p, 62%) and greatest for dry matter laid down before or during early stem elongation (average value for h2-M, 95% and for h2-P 88%). Even though heritability for grain - was also relatively high (average value for h2-M, 92% and for h2-P, 79%), genotypic differences in grain - are difficult to interpret because of the likelihood of some changes in genotype ranking for - resulting from differences among genotypes in the degree of water stress encountered during grain filling. As well, the contribution of remobilized carbon to grain - may vary between environments and genotypes. We conclude that, for wheat, assessment of genotypic variation in - should be most effective under well-watered conditions using dry matter laid down early in plant development.

The effect of variation in soil water availability, vapour pressure deficit and nitrogen nutrition on carbon isotope discrimination in wheat

1992 ◽  
Vol 43 (5) ◽  
pp. 935 ◽  
Author(s):  
AG Condon ◽  
RA Richards ◽  
GD Farquhar
Keyword(s):  
Field Experiment ◽  
Soil Water ◽  
Carbon Isotope ◽  
Vapour Pressure ◽  
Dry Matter ◽  
Carbon Isotope Discrimination ◽  
Nitrogen Nutrition ◽  
Vapour Pressure Deficit ◽  
Isotope Discrimination ◽  
Plant Parts

Carbon isotope discrimination (-) is an integrative measure of leaf transpiration efficiency and has been proposed as a select criterion for greater water-use efficiency in breeding programs for water-limited environments. Here we assess the effects of variation in soil water status, vapour pressure deficit and nitrogen nutrition on the value of - measured in plant dry matter and the relative magnitudes of environmental and genotypic variation in - among conventional wheat cultivars. Experiments were done using container- and field-grown plants. Two genotypes, cv. Cleopatra and Yaqui 50E, were grown in large (23 L) containers to simulate field conditions. Plants were subjected to contrasting watering regimes, to different levels of atmospheric demand (by growing the plants outdoors and varying sowing time) and to two levels of nitrogen nutrition (equivalent to 150 and 30 kg N ha-1). A field experiment using eight genotypes was conducted at Moombooldool in south-west New South Wales, which has an annual rainfall total and distribution typical of much of the south-east wheat belt. Changes in - over the course of the season were followed by sampling recently expanded plant parts. In field-grown plants A measured in dry matter fell by 5x10-3 between early-formed leaves and the grain. A similar change (7x10-3) was observed in container-grown plants. For both field- and container-grown plants, environmental effects on - were attributed to stomatal closure in response to declining soil water and/or increasing vapour-pressure deficit. Low nitrogen nutrition of container-grown plants, which reduced above-ground dry matter at maturity and leaf area at flag leaf emergence by 30%, had a small but variable effect on thevalue of -. In the field experiment, variation among genotypes in - of different plant parts was always significant, and was typically c. l.8 x l 0-3 . Genotype ranking for - changed with different plant parts, but the magnitude of genotype x environment interaction was small in relation to genetic variation in -. Changes in ranking mainly occurred in the latter half of the season. These were attributed primarily to differences in the rate and extent of soil drying among genotypes. Variation in the extent of soil water depletion measured at anthesis was positively correlated with - of plant parts laid down early in the season.

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).

Growth, chemical composition, and carbon isotope discrimination of pistachio (Pistacia vera L.) rootstock seedlings in response to salinity

2005 ◽  
Vol 56 (2) ◽  
pp. 135 ◽  
Author(s):  
H. Hokmabadi ◽  
K. Arzani ◽  
P. F. Grierson
Keyword(s):  
Carbon Isotope ◽  
Carbon Isotope Discrimination ◽  
Weight Ratio ◽  
Root Systems ◽  
Growth Responses ◽  
Isotope Discrimination ◽  
Significant Difference ◽  
History Of ◽  
Net Assimilation ◽  
K Concentration

Pistachio is considered a potential crop for many semi-arid regions affected by salinisation. We examined the effects of salinity on growth of 3 pistachio rootstocks: Badami-e-zarand, Sarakhs, and Ghazvini. Rootstocks were grown in soil in 8-L polyethylene pots and irrigated every 3 days with treatments of 0, 75, 150, or 225 mm NaCl. We measured above-ground biomass, allocation of C to root systems and foliage, and carbon isotope discrimination (Δ) and proline accumulation after 30 days and again after 60 days. Relative growth rate (RGR) decreased with time for all treatments and rootstocks. RGR and net assimilation rates (NARw) decreased with increasing salinity. In all rootstocks, NARw, but not leaf weight ratio (LWR), was significantly correlated with RGR, indicating that NARw was an important factor underlying growth responses among rootstocks. Increased salinity did not affect leaf water potential (Ψleaf), even though proline concentrations increased with increasing NaCl concentration, particularly in the Ghazvini rootstocks. Both Cl– and Na+ concentrations in leaves increased from 30 to 60 days but not in roots and stems. The Sarakhs rootstocks accumulated more of Cl– and Na+ compared with other rootstocks. K+ concentration in the roots and stems of all rootstocks also decreased with increasing salinity at both 30 and 60 days. Concentrations of Ca2+ in stems and root systems, but not in leaves, were also reduced by increased salinity in all rootstocks but only after 60 days. Carbon isotope discrimination (Δ) decreased with increased salinity in the leaves, stems, and roots; however, there was no significant difference in carbon isotope discrimination among rootstocks. We conclude that the Ghazvini rootstock was the most salt tolerant among the rootstocks tested. Carbon isotope discrimination in pistachio rootstocks may be a useful indicator of cumulative salinity history of the plant but is not a suitable indicator for pre-screening of pistachio rootstocks for salinity resistance.

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