Primary Root Formation in the Growing Shoots of Several Cereal Crops

Abstract

Formation and morphology of the primary roots on growing shoots were observed in field grown cereals, i.e. Setaria italica Beauv., Panicum miliaceum L., Echinochloa frumentacea Link., Pennisetum typhoideum Rich., sorghum bicolor Moench., Coix lachrymajobi L. and Eleusine coracana Gaertn. All species showed a similar developmental pattern. Although root emergence proceeded keeping pace with leaf emergence, the pace varied from species to species. Among species we also found some morphological differences such as, stem diameters, the number and diameters of the primary roots, and frequency of the secondary roots along the primary root axes. In all species examined, the basal diameter of the primary roots was closely correlated with the diameter of the stem on which they appeared. The root diameter acropetally decreased rapidly in any root parts where the diameter is large. The results were discussed from two aspects, namely, the determining process of the number of the primary roots and formative process of each primary root.