The arc mutants of Arabidopsis with fewer large chloroplasts have a lower mesophyll conductance.
Photosynthetic cells of most land plant lineages have numerous small chloroplasts even though most algae, and even the early diverging land plant group the hornworts, tend to have one or a few large chloroplasts. One constraint that small chloroplasts could improve is the resistance to CO2 diffusion from the atmosphere to the chloroplast stroma. We examined the mesophyll conductance (inverse of the diffusion resistance) of mutant Arabidopsis thaliana plants with one or only a few large chloroplasts per cell. The accumulation and replication of chloroplasts (arc) mutants of A. thaliana were studied by model fitting to gas exchange data and (13)CO2 discrimination during carbon fixation. The two methods generally agreed, but the value of the CO2 compensation point of Rubisco (Γ *) used in the model had a large impact on the estimated photosynthetic parameters, including mesophyll conductance. We found that having only a few large chloroplasts per cell resulted in a 25-50 % reduction in the mesophyll conductance at ambient CO2.
Department of Biochemistry & Molecular Biology, Michigan State University, 603 Wilson Road, Room 201, East Lansing, MI, 48824, USA.
Sean E
SE
Weise
David J
DJ
Carr
Ashley M
AM
Bourke
David T
DT
Hanson
Debbie
D
Swarthout
Thomas D
TD
Sharkey
D017360:Arabidopsis / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000378:metabolism*; D002245:Carbon Dioxide / Q000378:metabolism; D002247:Carbon Isotopes; D002736:Chloroplasts / Q000378:metabolism*; D005453:Fluorescence; D058503:Mesophyll Cells / Q000378:metabolism*; D008954:Models, Biological; D009154:Mutation / Q000235:genetics*; D010788:Photosynthesis; D012273:Ribulose-Bisphosphate Carboxylase / Q000378:metabolism; D014026:Nicotiana / Q000378:metabolism
D029681:Arabidopsis Proteins; D002247:Carbon Isotopes; D002245:Carbon Dioxide; D012273:Ribulose-Bisphosphate Carboxylase