Differential genotypic and root type responses to aluminum toxic and compacted subsoil layers using neutron radiography

Most adverse soil conditions, including aluminum toxicity and subsoil compaction, are perceived by the plant through its roots. Tolerance to Al-toxicity and compacted subsoil conditions has been developed in crop species. The resulting cultivars, however, do not always express this tolerance under different environments. Although root types of some crops have been observed to respond differently to the same soil stress conditions, plant root type responses to Al-toxic and/or compacted subsoil have not been thoroughly documented.;A set of genetic lines within two different species was investigated to determine tap, basal, and lateral root response to Al-toxic and/or compacted subsoil conditions. Maize and soybean cultivars reported to be tolerant to either Al-toxic or subsoil compacted conditions were grown in containers with Al-toxic Porter (pH 4.5 and 92% Al saturation) or compacted subsoil (1.65 Mg m;Neutron radiographic images of maize and soybean roots revealed that the tap, basal, and lateral root lengths of maize cv. CMS-36 were not significantly affected by Al-toxic Porter subsoil, illustrating their tolerance to the toxicity of this soil. Root elongation in the Al-toxic Porter subsoil suggests that, in the soybean line PI 416937, tap and lateral roots are Al-tolerant, and basal roots are only moderately Al-tolerant. Although basal roots of the maize cv. SA-3 and soybean cv. Davis were found to be Al-tolerant, tap and lateral root lengths were severely reduced in the Al-toxic subsoil. The subsoil compaction experiment demonstrated that taproots of maize SA-3 and soybean PI 416937 penetrated the compacted subsoil layer, while only basal roots of maize cv. La Posta and soybean cv. Weber penetrated the compacted layer. On the other hand, soybean cv. Perry moderately penetrated the compacted subsoil layer with both tap and basal roots.;These experiments demonstrate that different maize and soybean root types can respond independently under Al-toxic and compacted subsoil conditions and that these observed root type responses can vary among genotypes within, as well as between species. This research suggests that it is essential to consider different root types as distinct entities when evaluating plant tolerance to adverse soil conditions.