Growth and yield responses of castor bean (Ricinus communis L.) at two enhanced CO<sub>2</sub> levels

Abstract

Growth and yield responses of castor bean (<I>Ricinus communis</I> L.) to two elevated CO<sub>2</sub> levels (550 and 700 ppm) were evaluated up to the maturity of first order spikes in open top chambers (OTCs). The growth characteristics – root and shoot lengths, root volume, root:shoot ratios, leaf area, dry weights of different plant parts, leaf area duration and crop growth rate increased with 550 and 700 ppm of CO<sub>2</sub> levels compared with ambient control. The spike length, pod and seed yield of first order spikes increased under enhanced CO<sub>2</sub> levels over ambient control. Elevated CO<sub>2</sub> levels significantly increased the total biomass and yield of castor bean, however enhanced CO<sub>2</sub> levels <I>per se</I> did not changed the content and quality of the castor oil. A positive response of castor bean to increased CO<sub>2</sub> concentrations is a good indication for its future existence in potentially changed climatic conditions.