Elevated CO2 increases wheat CER, leaf and tiller development, and shoot and root growth

Whole-plant responses to elevated CO2 throughout the life cycle are needed to understand future impacts of elevated atmospheric CO2. In this study, Tr iticum aestivum L. leaf carbon exchange rates (CER) and carbohydrates, grow th, and development were examined at the tillering, booting, and grain-fill ing stages in growth chambers with CO2 concentrations of 350 (ambient) or 7 00 thigh) mu mol mol(-1). Single-leaf CER values measured on plants grown a t high CO2 were 50% greater than those measured on plants grown at ambient CO2 for all growth stages, with no photosynthetic acclimation observed at h igh CO2. Leaves grown in high CO2 had more starch and simple sugars at till ering and booting, and more starch at grain-filling, than those grown in am bient CO2. CER and carbohydrate levels were positively correlated with leaf appearance rates and tillering (especially third-, fourth- and fifth-order tillers). Elevated CO2 slightly delayed tiller appearance, but accelerated tiller development after appearance. Although high CO2 increased leaf appe arance rates, final leaf number/culm was not effected because growth stages were reached slightly sooner. Greater plant biomass was related to greater tillering. Doubling CO2 significantly increased both shoot and root dry we ight, but decreased the shoot to root ratio. High CO2 plants had more spike s plant(-1) and spikelets spike(-1), but a similar number of fertile spikel ets spike(-1). Elevated CO2 resulted in greater shoot, root and spike produ ction and quicker canopy development by increasing leaf and tiller appearan ce rates and phenology.