Opposite carbon isotope discrimination during dark respiration in leaves versus roots - a review

2013 ◽  
Vol 201 (3) ◽  
pp. 751-769 ◽  
Author(s):  
Jaleh Ghashghaie ◽  
Franz W. Badeck
Keyword(s):  
Carbon Isotope ◽  
Carbon Isotope Discrimination ◽  
Dark Respiration ◽  
Isotope Discrimination

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 An observational constraint on stomatal function in forests: evaluating coupled carbon and water vapor exchange with carbon isotopes in the Community Land Model (CLM4.5)

2016 ◽  
Vol 13 (18) ◽  
pp. 5183-5204 ◽  
Author(s):  
Brett Raczka ◽  
Henrique F. Duarte ◽  
Charles D. Koven ◽  
Daniel Ricciuto ◽  
Peter E. Thornton ◽  
...  
Keyword(s):  
Stomatal Conductance ◽  
Carbon Isotope ◽  
Carbon Isotopes ◽  
Nitrogen Limitation ◽  
Carbon Isotope Discrimination ◽  
Stable Carbon Isotope ◽  
Atmospheric Co2 ◽  
Stable Carbon ◽  
Isotope Discrimination ◽  
Community Land Model

Abstract. Land surface models are useful tools to quantify contemporary and future climate impact on terrestrial carbon cycle processes, provided they can be appropriately constrained and tested with observations. Stable carbon isotopes of CO2 offer the potential to improve model representation of the coupled carbon and water cycles because they are strongly influenced by stomatal function. Recently, a representation of stable carbon isotope discrimination was incorporated into the Community Land Model component of the Community Earth System Model. Here, we tested the model's capability to simulate whole-forest isotope discrimination in a subalpine conifer forest at Niwot Ridge, Colorado, USA. We distinguished between isotopic behavior in response to a decrease of δ13C within atmospheric CO2 (Suess effect) vs. photosynthetic discrimination (Δcanopy), by creating a site-customized atmospheric CO2 and δ13C of CO2 time series. We implemented a seasonally varying Vcmax model calibration that best matched site observations of net CO2 carbon exchange, latent heat exchange, and biomass. The model accurately simulated observed δ13C of needle and stem tissue, but underestimated the δ13C of bulk soil carbon by 1–2 ‰. The model overestimated the multiyear (2006–2012) average Δcanopy relative to prior data-based estimates by 2–4 ‰. The amplitude of the average seasonal cycle of Δcanopy (i.e., higher in spring/fall as compared to summer) was correctly modeled but only when using a revised, fully coupled An − gs (net assimilation rate, stomatal conductance) version of the model in contrast to the partially coupled An − gs version used in the default model. The model attributed most of the seasonal variation in discrimination to An, whereas interannual variation in simulated Δcanopy during the summer months was driven by stomatal response to vapor pressure deficit (VPD). The model simulated a 10 % increase in both photosynthetic discrimination and water-use efficiency (WUE) since 1850 which is counter to established relationships between discrimination and WUE. The isotope observations used here to constrain CLM suggest (1) the model overestimated stomatal conductance and (2) the default CLM approach to representing nitrogen limitation (partially coupled model) was not capable of reproducing observed trends in discrimination. These findings demonstrate that isotope observations can provide important information related to stomatal function driven by environmental stress from VPD and nitrogen limitation. Future versions of CLM that incorporate carbon isotope discrimination are likely to benefit from explicit inclusion of mesophyll conductance.

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