Response of determinate- and semi-determinate-types of common bean to elevated CO2 concentration in the atmosphere

Abstract

The growth of determinate-type and semi-determinate -type plants of common beam (Phaseolus vulgaris L.) was studied at elevated (700 μL L-1) and ambient (350 μL Lp-1) CO, concentrations in an open-top chamber. Successive changes in dry matter production and in the number of stems and branches were investigated. To evaluate the sink-source balance at different CO2 concentrations, 13CO2 was introduced to the leaves during the pod filling stage and the 13C distribution profile was analyzed. In the elevated CO2 treatment, no significant differences in dry matter production were observed for the determinate -type plants, unlike in the semi-determinate-type ones, where the volume was 1.3 times bigger than those in the ambient CO2 treatment. This enhanced growth in the semi-determinatetype plants mainly involved the branches. Starch accumulation in leaves at elevated CO2 concentratton was up to 200 and 300 mg glucose g DML-1 for determinate- and semi-determinate-types, respectively. Though the increased accumulation of starch under elevated CO2 treatment was more pronounced in the semi-determinate-type plants, it appeared that photosynthesis was not down-regulated. The net assimilation rate of the semi-determinate-type plants in the elevated CO2 treatment was generally higher than that in the ambient CO2 treatment. The semi-determinate-type plants could take advantage of the elevated CO2 treatment for the distribution of photosynthates to branches, while in the determinate-type plants the growth of the branches could not be expanded, and consequently plant growth was not enhanced by elevated CO2 treatment.