Gas exchange analysis and online photosynthetic discrimination

Range Table - link
Organism Tobacco Nicotiana tabacum
Reference Uehlein N, Otto B, Hanson DT, Fischer M, McDowell N, Kaldenhoff R (2008) Function of Nicotiana tabacum aquaporins as chloroplast gas pores challenges the concept of membrane CO2 permeability. Plant Cell 20: 648–57 p.652 table 2PubMed ID18349152
Comments "At the assay light intensity of 2000 µmol photons/m^2/sec, A [net photosynthesis] was lower in the RNAi line, though only significant as a trend (P=0.10), while gs [stomatal conductance to water vapor] and ci [intercellular CO2 partial pressure] did not differ significantly between control and RNAi lines (Table 2). The ratio of A to ci in New Mexico–grown wild-type plants was ~25% higher than that of the wild-type plants grown in Germany, suggesting that the New Mexico plants either had a higher photosynthetic capacity (greater amounts or more active Rubisco) or a higher gi. Applying these data to the Evans et al. (1986) model, [researchers] calculated that the mesophyll conductance for CO2 (gi) in the RNAi line is 21% lower (or ri [resistance to CO2 diffusion inside leaves] is 27% higher) than for the control line. Since cc=ci-(A/gi), this equates with a 1.7 Pa (13%, P=0.16) lower cc in the RNAi line (Table 2). Lower rates of photosynthesis in the RNAi line have the effect of increasing the calculated cc, so it is not surprising that the cc decrease is only a trend." See note beneath table
Entered by Uri M
ID 110842