| Four types of potato roots have been described. Research has indicated that roots on the stolon and on the tuber itself may be particularly effective in transporting Ca, via the xylem, into the tuber. Experiments were designed to investigate (1) the proliferation of the different types of roots under field conditions, (2) xylem vs. phloem transport of nutrients of varying phloem mobility, and (3) the ability of different kinds of roots to transport Ca, Mn, and B to the potato (Solanum tuberosum L. cv. Russet Burbank) tuber.;Field studies indicated that tuber roots occurred infrequently. Stolon roots commonly occurred, but their effectiveness in supplying nutrients may be limited due to the small volume of soil they explore. Junction roots, which originate from stem nodes also giving rise to stolons, penetrated the soil as deeply as roots originating from the base of the stem. The xylem and phloem structure at these nodes is quite complex, with considerable intermingling of xylem and phloem tissues. The enhanced contact area between the two tissues would allow opportunity for xylem to phloem transfer or for root-xylem to stolon-xylem transfer. Either process would increase nutrient availability to the tuber. Thus, junction roots may play an important role in tuber nutrition because of their proximity to the tuber and the large volume of soil with which they are in contact.;Several potential xylem and phloem pathways exist for the transport of nutrients to the tuber. Phloem flow was an important factor in supplying the nutrients of interest to the tuber. No Ca, B, or Mn deficiencies were observed in the plants or tubers in the greenhouse under the split-root systems. It is likely that two or more transport pathways involving both phloem and xylem are involved in the supply of Ca, Mn and B to the tuber. |
