Bottom up mesophyll conductance under diverse light levels in Brassica carinata

Since its first publication the model by Farquhar et al. (1980) has triggered debates whether substomatal CO2 concentration can be significantly higher than that at the carboxylation site and, as such, the photosynthetic parameters Vcmax and Jmax calculated by the model might be biased. A number of studies were undertaken on this topic giving evidence that mesophyll conductance (gm) can significantly decrease the CO2 concentration at the Rubisco site to an extent depending on water and salinity stress, leaf age, mineral nutrition etc.. Irradiance significantly affects leaf anatomy and mesophyll architecture (Nobel, 1991; Parkhurst, 1994), hence it can be expected to influence gm as well. However, few studies have documented this aspect (see Flexas et al., 2008, for a recent review), and therefore this research addressed the influence of light upon gm in a plant profile of Brassica carinata.