Photosynthetic traits in wheat grown under decreased and increased CO2 concentration, and after transfer to natural CO2 concentration

Wheat plants were grown from sowing to day 18 in 26-dm(3) chambers at three different CO2 concentrations: 150 (-CO2), 350 (C, control), 800 (+CO2) mu mol mol(-1). Afterwards, plants of the thr ee variants were grown at the sa me natural CO2 concentration. Plant characteristics were measured just befo re the transfer (0 days after CO2 treatment, DAT), and at 5 - 8 DAT on the 1(st) leaf, and at 12 - 22 DAT on the 4(th) leaf. Decreased or increased CO 2 concentrations caused acclimations which persisted after transplantation to natural CO2 concentration. At 5 - 8 DAT, stomatal density, stomatal cond uctance (g(s)), CO2 saturated net photosynthetic rate (P-NsatC), radiation saturated net photosynthetic rate (P-Nsatl), and carboxylation efficiency ( tau) were higher in -CO2 plants and lower in +CO2 plants than in C plants. As compared with C plants, the photochemical efficiency (alpha) was lower in -CO2 and higher in +CO2 plants, however, chlorophyll (Chl) a, Chl b, Chl a+b and carotenoid contents were lower in both -CO2 and +CO2 plants. On th e 4(th) leaf, which emerged on plant after finishing CO2 treatments, at 12 - 22 DAT, no differences in stomatal density and g(s) between treatments we re observed. In -CO2 plants, pigment content and P-NsatC were higher, alpha was lower, and P-Nsatl and tau were not different from C plants. In contra st, in +CO2 plants, pigment content, P-Nsatl and tau were lower, and P-Nsat C and alpha were unchanged. Leaf area, dry mass, and tiller development inc reased in +CO2 plants and decreased in -CO2 plants. In the interval between 8 and 22 DAT, lower net assimilation rate in +CO2 than in -CO2 plants was observed.