Carbon isotope fractionation including photosynthetic and post-photosynthetic processes in C3 plants: Low [CO2] matters. (15th January 2019)

• Record Type: Journal Article
• Authors: Zhang, Hai-Yang; Hartmann, Henrik; Gleixner, Gerd; Thoma, Michael; Schwab, Valérie F.
• Is Part Of: Geochimica et cosmochimica acta. Volume 245(2019)
• Page Start: 1
• Page End: 15
• Publication Date: 2019-01-15
• Subjects: Cellulose -- PLFA -- n-Alkane -- Carbon isotopes -- Drought -- Plant metabolites -- Paleoclimate; Geochemistry -- Periodicals; Meteorites -- Periodicals; Géochimie -- Périodiques; Météorites -- Périodiques; Geochemie; Astrochemie; Electronic journals; 551.905
• DOI: 10.1016/j.gca.2018.09.035
• Languages: English
• ISSNs: 0016-7037

Abstract

Abstract: Carbon isotope ratios of plants are highly informative for the reconstruction of ancient environments and for the interpretation of plant physiological processes to climate, but their responses to changing atmospheric CO2 concentration are currently debated. Moreover, plants in the geological past have experienced long-term low CO2 concentration (LC). However, the effects of LC on the plant C isotope ratios are still elusive. To investigate effects of atmospheric CO2 concentration ([CO2 ]) and drought on isotope ratios of plant metabolites we grew winter wheat ( Triticum aestivum ) in climate-controlled chambers under different [CO2 ] covering glacial, pre-industrial, and present concentrations (170, 280, and 400 ppm) and water regimes (well-watered and drought). First, we quantified total C isotope discrimination between plant and atmosphere (Δ) using 13 C on-line measurements of plant gas exchange and 13 C values of plant metabolites, i.e., cellulose, n -alkane, and phospholipid fatty acids (PLFA). We found that LC yielded a higher Δ regardless of water regime, i.e. more 13 C-depleted values were found under LC; the effect was stronger for n -C29 alkane (1.5‰/100 ppm) and C16:0 PLFA (1.1‰/100 ppm) than that for cellulose (0.6‰/100 ppm). We then calculated post-photosynthetic C isotope shift (ɛ) between specific metabolites and plant bulk isotope values. δ 13 C n -C29 alkane and δ 13 CPLFA were 8.3‰ and 7.3‰ lighter than the δ 13 Cbulk under 400 ppm; these depletions became higher (9.8‰ and 8.2‰ lighter than the δ 13 Cbulk for n -C29 alkane and PLFA, respectively) under 170 ppm. In contrast, δ 13 Ccellulose was 1.2‰ heavier than the δ 13 Cbulk under 400 ppm while this enrichment became higher (1.6‰) under 170 ppm. Changes in atmospheric [CO2 ] affected C fractionation not only via photosynthetic but also post-photosynthetic processes and thus must be taken into account when interpreting C isotopes for paleoclimate reconstruction and future global C cycle prediction.