Steep, Deep, and Cheap: New Evidence Supports the Root Ideotype.

New evidence supports the validity of the “Steed, deep, and cheap” ideotype for efficient acquisition of mobile soil resources by maize roots. Steeply angled brace and crown roots allow root growth to follow the nitrate leaching through the soil profile and also permit the roots to access deeper soil horizons, where water may be more abundant during drought events. Formation of root cortical aerenchyma (RCA) reduces root respiration costs, thus permitting deeper root growth, and facilitating increased vigor in drought and low nitrogen environments. Significant genetic variation for these phenes exists in maize, and rapid  phenotyping methods should increase the utility of these phenes for the improvement of maize for low-input systems.