Synergism of Root Architectural and Anatomical Phenes In Maize.

Plants often respond to low fertility or drought by increasing their investment in root growth at the cost of aboveground growth, including reproductive development. Reducing the increasing/increased cost of soil resource acquisition may be an effective strategy  in breeding drought and low fertility tolerant crops. We have previously reported on root architectural and root anatomical phenes that reduce the cost of resource acquisition. However, thus far we have explored the utility of these phenes in isolation. It is possible that the utility of anatomical phenes may depend on the architectural of phenes with which they occur. Here we used SimRoot, a functional-structural plant model, to test for synergism between architectural and anatomical traits in Maize. We focused on the architectural trait crown root number, and the anatomical trait root cortical aerenchyma across a range of nitrogen availability scenarios. With greater nitrogen availability, increasing number of crown roots led to deeper rooting and increased total root length, while greater formation of root cortical aerenchyma had little effect on either root length or rooting depth. With low nitrogen availability, total root length was greatest for plants with intermediate numbers of crown roots, and increased formation of root cortical aerenchyma increased total root length in these plants. These results suggest that there is synergism between architectural and anatomical phenes in roots. Utility of an integrated phenotype should be greatest when phenes that reduce the cost of soil exploration (such as formation of root cortical aerenchyma) occur with phenes that increase soil exploration (crown root number).