Root growth and functioning under atmospheric CO2 enrichment

This paper examines the extent to which atmospheric CO2 enrichment may influence growth of plant roots and function in terms of uptake of water and nutrients, and carbon allocation towards symbionts. It is concluded that changes in dry matter allocation greatly depend on the experimental conditions during the experiment, the growth phase of the plant, and its morphological characteristics. Under non-limiting conditions of water and nutrients for growth, dry matter partitioning to the root is not changed by CO2 enrichment. The increase in root/shoot ratio, frequently observed under limiting conditions of water and/or nutrients, enables the plant to explore a greater soil volume, and hence acquire more water and nutrients. However, more data on changes in dry matter allocation within the root due to atmospheric CO2 are needed. It is concluded that nitrogen fixation is favored by CO2 enrichment since nodule mass is increased, concomitant with an increase in root length. The papers available so far on the influence of CO2 enrichment on mycorrhizal functioning suggest that carbon allocation to the roots might be increased, but also here more experiments are needed.