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Summary Traditionally, leaves were thought to be supplied withCO2for photosynthesis by the atmosphere and respiration. Recent studies, however, have shown that the xylem also transports a significant amount of inorganic carbon into leaves through the bulk flow of water. However, little is known about the dynamics and proportion of xylem‐transportedCO2that is assimilated, vs simply lost to transpiration.Cut leaves ofPopulus deltoidesandBrassica napuswere placed in eitherKCl or one of three [NaH13CO3] solutions dissolved in water to simultaneously measure the assimilation and the efflux of xylem‐transportedCO2exiting the leaf across light andCO2response curves in real‐time using a tunable diode laser absorption spectroscope.The rates of assimilation and efflux of xylem‐transportedCO2increased with increasing xylem [13CO2*] and transpiration. Under saturating irradiance, rates of assimilation using xylem‐transportedCO2accounted forc.2.5% of the total assimilation in both species in the highest [13CO2*].The majority of xylem‐transportedCO2is assimilated, and efflux is small compared to respiration. Assimilation of xylem‐transportedCO2comprises a small portion of total photosynthesis, but may be more important whenCO2is limiting.
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Rising atmospheric CO 2 concentration inhibits nitrate assimilation in shoots but enhances it in roots of C 3 plants
We have proposed that rising atmospheric CO2concentrations inhibit malate production in chloroplasts and thus impede assimilation of nitrate into protein in shoots of C3plants, a phenomenon that will strongly influence primary productivity and food security under the environmental conditions anticipated during the next few decades. Although hundreds of studies support this proposal, several publications in 2018 and 2019 purport to present counterevidence. The following study evaluates these publications as well as presents new data that elevated CO2enhances root nitrate assimilation in wheat andArabidopsiswhile it inhibits shoot nitrate assimilation.
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- PAR ID:
- 10458348
- Publisher / Repository:
- Wiley-Blackwell
- Date Published:
- Journal Name:
- Physiologia Plantarum
- Volume:
- 168
- Issue:
- 4
- ISSN:
- 0031-9317
- Format(s):
- Medium: X Size: p. 963-972
- Size(s):
- p. 963-972
- Sponsoring Org:
- National Science Foundation
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