REGULAR ARTICLE The plasticity of the growth and proliferation of wheat root system under elevated CO 2 María Benlloch-Gonzalez & Jens Berger & Helen Bramley & Greg Rebetzke & Jairo A. Palta Received: 14 April 2013 / Accepted: 3 October 2013 # Springer Science+Business Media Dordrecht 2013 Abstract Background and Aims Understanding crop responses to increasing atmospheric CO 2 requires knowledge of how their root systems grow, proliferate and function. The effect of elevated CO 2 on the growth and prolifer- ation of wheat root system (Triticum aestivum L.), was examined. Methods Two pairs of sister lines of wheat contrasting in vigour (CV97 and CV207) and tillering (7750N and 7750PF) were grown in rhizo-boxes under ambient (380 μlL -1 ) and elevated CO 2 (700 μlL -1 ), and the root growth and proliferation mapped. Results Elevated CO 2 effects on shoot and root bio- mass were observed in the lines contrasting for vigour, but not in the lines contrasting for tillering. Root bio- mass was reduced by 67 % in the high vigour line CV97, reducing total plant biomass by 26 % compared to the low vigour line, CV207. This was due to a reduction in root length down the 1 m soil profile and root proliferation in the top 0.2 m layer. The reduction in root biomass was not compensated by an increase in shoot biomass. Conclusions The reduction in root biomass under ele- vated CO 2 in the vigour line CV97 can be explained through its inability to increase the sink strength due to the failure to increase tiller number to which the plant presumably responded by increasing losses of the new- ly assimilated carbon by respiration. Keywords Vigorous wheat . Restricted tillering . Rhizo-boxes . Root proliferation . Root length . Future climate Introduction The growth and proliferation of the root system deter- mines a plant’ s ability to capture water and nutrients, particularly N and P (Liao et al. 2006; Palta and Watt 2009). Future climate predictions for many agricultural regions (i.e. increasing atmospheric [CO 2 ] and temper- ature, and reducing rainfall) are expected to influence crop production. Most studies on the potential impacts of climate change have focused on above-ground traits (Reynolds-Henn et al. 2010; Wertin et al. 2010), but growth and development of root systems may also be Plant Soil DOI 10.1007/s11104-013-1934-3 Responsible Editor: Martin Weih. M. Benlloch-Gonzalez Departamento de Agronomía, Escuela Técnica Superior de Ingenieros Agrónomos y Montes, Universidad de Córdoba, Campus de Excelencia Internacional Agroalimentario, ceiA3, Ctra. Madrid-Cádiz, Km. 396, 14071 Córdoba, Spain M. Benlloch-Gonzalez : J. Berger : J. A. Palta (*) CSIRO, Plant Industry, Private Bag No. 5, Wembley, WA 6913, Australia e-mail: jairo.palta@csiro.au H. Bramley : J. A. Palta The UWA Institute of Agriculture, The University of Western Australia, 35 Stirling Highway, Crawley, WA 6009, Australia G. Rebetzke CSIRO Plant Industry, PO Box 1600, Canberra, ACT 2601, Australia