Little or no information is available on the contribution of individual subterranean nodes to the storage root formation in sweet potatoes. Therefore, two field trials were conducted where apical vine cuttings of various cultivars were planted vertically or horizontally, with three or five nodes beneath the soil surface, and storage root formation was monitored. The same potential for storage root formation existed at the various subterranean nodes provided that the plant material had been cut equidistant from the two nodes. The differentiation of potential storage roots at the basal node was stimulated when vines were cut directly below a node. Only a small percentage of these roots eventually developed into storage roots. The number, length and diameter of the storage roots, as well as the storage root stalk length decreased progressively at the lower nodes. There was no benefit in planting at depths where more than three nodes were below the soil surface. The limited differentiation and development of storage roots at the lower nodes may be ascribed to soil physical factors, although factors such as assimilate partitioning may also play an important role.
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