Storage roots normally arise from the underground portion of a vine (stem) cutting to be used as planting material. The most economically important physiological process in sweetpotato production is storage root (SR) development. Sweetpotato is a crop of immense potential because it yields more “edible” energy on marginal land than any other major food crop and can withstand adverse abiotic and biotic stresses ( Mukhopadhyay et al., 2011). Sweetpotato, with cassava ( Manihot esculenta Crantz) and potato ( Solanum tuberosum L.), are among the major root and tuber crops, which are second in importance to cereals as a global source of carbohydrates ( Villordon et al., 2014 and references therein). This system can serve for studying the effect of environmental conditions on AR initiation, development, and capacity to form storage roots. The mechanism regulating AR initiation in nodes is discussed. Adventitious roots originating from nodes 9–13 possess similar AR systems and develop better than those originating from younger nodes 3–8. Conclusions: Nodal position (age) has a significant effect on the developmental status and number of root primordia inside the stem, determining the number and length of ARs that have developed by 14 DAP.The total length of established roots at nodes 9–13 from the apex is about 2-fold longer than at nodes 5–8. The number of ARs that develop from isolated stem nodes 14 DAP corresponded to the number of AR primordia detected inside the stem.

Key results: Primordia for ARs initiate at the junction of the stem pith ray and the cambium, on both sides of the leaf gap, and they are well developed before emerging from the stem.Methods: We anatomically described root primordium initiation using stem sections and measured number of root primordia formed at different nodal positions using light microscopy and correlated nodal positions with AR number and length 14 d after planting (DAP).Data on the origin of sweetpotato ARs and the effect of nodal position on AR establishment and further development are limited. Storage roots develop from adventitious roots (ARs) present in stem cuttings that serve as propagation material. Premise of the study: Yield in sweetpotato is determined by the number of storage roots produced per plant.

Root primordia tomato plant