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Title: Mesophyll conductance in Zea mays responds transiently to CO 2 availability: implications for transpiration efficiency in C 4 crops

 [1];  [1]
  1. School of Biological Sciences, Washington State University, Pullman WA 99164 USA
Publication Date:
Sponsoring Org.:
USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23)
OSTI Identifier:
Grant/Contract Number:
Resource Type:
Journal Article: Publisher's Accepted Manuscript
Journal Name:
New Phytologist
Additional Journal Information:
Journal Volume: 217; Journal Issue: 4; Related Information: CHORUS Timestamp: 2018-02-06 07:25:01; Journal ID: ISSN 0028-646X
Country of Publication:
United Kingdom

Citation Formats

Kolbe, Allison R., and Cousins, Asaph B. Mesophyll conductance in Zea mays responds transiently to CO 2 availability: implications for transpiration efficiency in C 4 crops. United Kingdom: N. p., 2017. Web. doi:10.1111/nph.14942.
Kolbe, Allison R., & Cousins, Asaph B. Mesophyll conductance in Zea mays responds transiently to CO 2 availability: implications for transpiration efficiency in C 4 crops. United Kingdom. doi:10.1111/nph.14942.
Kolbe, Allison R., and Cousins, Asaph B. 2017. "Mesophyll conductance in Zea mays responds transiently to CO 2 availability: implications for transpiration efficiency in C 4 crops". United Kingdom. doi:10.1111/nph.14942.
title = {Mesophyll conductance in Zea mays responds transiently to CO 2 availability: implications for transpiration efficiency in C 4 crops},
author = {Kolbe, Allison R. and Cousins, Asaph B.},
abstractNote = {},
doi = {10.1111/nph.14942},
journal = {New Phytologist},
number = 4,
volume = 217,
place = {United Kingdom},
year = 2017,
month =

Journal Article:
Free Publicly Available Full Text
This content will become publicly available on December 8, 2018
Publisher's Accepted Manuscript

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  • Worldwide measurements of nearly 130 C3 species covering all major plant functional types are analyzed in conjunction with model simulations to determine the effects of mesophyll conductance (gm) on photosynthetic parameters and their relationships estimated from A/Ci curves. We find that an assumption of infinite gm results in up to 75% underestimation for maximum carboxylation rate Vcmax, 60% for maximum electron transport rate Jmax, and 40% for triose phosphate utilization rate Tu. Vcmax is most sensitive, Jmax is less sensitive, and Tu has the least sensitivity to the variation of gm. Due to this asymmetrical effect of gm, the ratiosmore » of Jmax to Vcmax, Tu to Vcmax, and Tu to Jmax are all overestimated. An infinite gm assumption also limits the freedom of variation of estimated parameters and artificially constrains parameter relationships to stronger shapes. These findings suggest the importance of quantifying gm for understanding in-situ photosynthetic machinery functioning. We show that a nonzero resistance to CO2 movement in chloroplasts has small effects on estimated parameters. A nonlinear function with gm as input is developed to convert the parameters estimated under an assumption of infinite gm to proper values. This function will facilitate gm representation in global carbon cycle models.« less
  • Studies with the variable J method have reported that mesophyll conductance (gm) rapidly decreases with increasing intercellular CO2 partial pressures (Ci) or decreasing irradiance. Similar responses have been suggested with the online isotope discrimination method, although with less consistency. Here we show that even when the true gm is constant, the variable J method can produce an artifactual dependence of gm on Ci or irradiance similar to those reported in previous studies for any of the following factors: day respiration and chloroplastic CO2 photocompensation point are estimated with Laisk method; Ci or electron transport rate is positively biased; net photosyntheticmore » rate is negatively biased; insufficient NADPH is assumed while insufficient ATP limits RuBP regeneration. The isotopic method produces similar artifacts if fractionation of carboxylation or Ci are positively biased or 13 negatively biased. A nonzero chloroplastic resistance to CO2 movement results in a qualitatively different dependence of gm on Ci or irradiance and this dependence is only sensitive at low Ci. We thus cannot rule out the possibility that previously reported dependence of gm on Ci or irradiance is a methodological artifact. Recommendations are made to take advantage of sensitivities of the variable J and isotopic methods for estimating gm.« less
  • Corn (Zea mays L.) and soybean (Glycine max L.) plants grown in media containing a range of Pb concentrations supplied as PbCl/sub 2/, showed decreased net photosynthesis and transpiration with increasing Pb treatment levels. At lower Pb treatment levels, corn appears to be more sensitive than soybeans. However, at high treatment levels (62.5-250 mg/plant) soybeans are more sensitive than corn. At 250 mg Pb/plant in the medium, photosynthesis is only 10% of maximum in soybeans but 47% in corn, even though corn Pb tissue content is much higher than that of soybeans. Transpiration exhibited similar trends to photosynthesis suggesting that,more » especially in corn, an appreciable part of the inhibition of the two processes is related to increased stomatal resistances with increased Pb concentrations. Lead accumulation trends were similar at treatment levels of 0 to 62.5 mg/plant but were slightly different at higher levels. The total amount of Pb accumulated was higher in corn than in soybeans. Maximum accumulation in both species occurred at 62.5 mg Pb/plant. 15 references, 3 figures.« less
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  • Soil water depletion by profile depth increments and total water usage were measured yearly under either small grains or corn (Zea mays L.) over a 4-yr period on undisturbed Williams loam (fine-loamy, mixed Typic Argiborolls) and soil reclaimed following simulated stripmining. The reclaimed soil had topsoil thickness of either 0.23, 0.46, or 0.69 m respread over nonsaline, nonsodic spoil materials whose textures were gravelly loamy sand with and without a clay loam subsoil, clay loam, or silty clay loam. Total water usage and soil water depletion (for profile depths of 0 to 0.6 m and 0.6 to 1.5 m) weremore » consistently greater, but essentially significant only in 1 yr, for the undisturbed compared to the reclaimed soil (averaged over topsoil thickness or spoil texture). Grain or biomass yields were significantly higher for the undisturbed compared with the reclaimed soil when growing-season precipitation was inadequate or poorly distributed. Shallower rooting depths and thus lesser soil water depletion even though the reclaimed soil had similar amounts of plant-available soil water at planting for 3 of the 4 yr resulted in water stress conditions and reduced potential productivity in inadequate precipitation years on the reclaimed soil. Similar water-use efficiency values were found for both the undisturbed and reclaimed soils for all 4 yr. If amounts of available soil water at planting and soil water depletion values had been more uniform between the undisturbed and reclaimed soils, the reclaimed soil most likely would have met the reclamation law requirement of equal or better than productivity present prior to mining (undisturbed soil productivity) for all 4 yr.« less