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

Abstract

Whole‐plant responses to elevated CO2 throughout the life cycle are needed to understand future impacts of elevated atmospheric CO2. In this study, Triticum aestivum L. leaf carbon exchange rates (CER) and carbohydrates, growth, and development were examined at the tillering, booting, and grain‐filling stages in growth chambers with CO2 concentrations of 350 (ambient) or 700 (high) μmol mol−1. Single‐leaf CER values measured on plants grown at high CO2 were 50% greater than those measured on plants grown at ambient CO2 for all growth stages, with no photosynthetic acclimation observed at high CO2. Leaves grown in high CO2 had more starch and simple sugars at tillering and booting, and more starch at grain‐filling, than those grown in ambient 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 appearance 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 weight, but decreased the shoot to root ratio. High CO2 plants had more spikes plant−1 and spikelets spike−1, but a similar number of fertile spikelets spike−1. Elevated CO2 resulted in greater shoot, root and spike production and quicker canopy development by increasing leaf and tiller appearance rates and phenology.