21251018
not annotated - annotated - LINNAEUS only
Using tunable diode laser spectroscopy to measure carbon isotope discrimination and mesophyll conductance to CO2 diffusion dynamically at different CO2 concentrations.
In C3 leaves, the mesophyll conductance to CO2 diffusion, g(m) , determines the drawdown in CO2 concentration from intercellular airspace to the chloroplast stroma. Both g(m) and stomatal conductance limit photosynthetic rate and vary in response to the environment. We investigated the response of g(m) to changes in CO2 in two Arabidopsis genotypes (including a mutant with open stomata, ost1), tobacco and wheat. We combined measurements of gas exchange with carbon isotope discrimination using tunable diode laser absorption spectroscopy with a CO2 calibration system specially designed for a range of CO2 and O2 concentrations. CO2 was initially increased from 200 to 1000 ppm and then decreased stepwise to 200 ppm and increased stepwise back to 1000 ppm, or the sequence was reversed. In 2% O2 a step increase from 200 to 1000 ppm significantly decreased g(m) by 26-40% in all three species, whereas following a step decrease from 1000 to 200 ppm, the 26-38% increase in g(m) was not statistically significant. The response of g(m) to CO2 was less in 21% O2. Comparing wild type against the ost1 revealed that mesophyll and stomatal conductance varied independently in response to CO2. We discuss the effects of isotope fractionation factors on estimating g(m) .
Ann file
T1 Species 567 574 tobacco
T2 Species 579 584 wheat
N1 Reference T1 Taxonomy:4097 Nicotiana tabacum
N2 Reference T2 Taxonomy:4565 Triticum aestivum
T3 Out-of-scope 499 510 Arabidopsis
N3 Reference T3 Taxonomy:3701 Arabidopsis