The xylem and phloem transport of mineral elements from stem nodal roots to the stem and stolon of growing potato (Solarium tuberosum L. cv. 'Russet Burbank') plants was investigated. Adventitious roots, originating from below-ground nodes of the stem of potato seedlings, were exposed to solutions of SrCl2 or MnS04. Relative elemental concentrations were measured in the conductive tissues using energy dispersive X-ray analysis. After a 5 h daylight uptake period, Sr (a Ca-transport analogue) levels were elevated in the stem xylem tissue, but Sr did not increase in the stem phloem, nor was it present in either of the conductive tissues of stolons located 1-2 nodes above the treated roots. In contrast, elevated levels of Cl, S, and Mn were found in stolon xylem and phloem tissue during the same period. The absence of Sr in the stolon after 5 h suggests that no xylem flow into the stolon occurred during the uptake period and, furthermore, phloem flow is responsible for the transport of the Cl, S, and Mn into the stolon. Elevated levels of these mobile nutrients in the xylem of the stolon were attributed to xylem-to-phloem transfer in the stem or leaves, transport to the stolon in the phloem, and phloem-to-xylem transfer in the stolon. During a 19 h uptake period, some Sr was observed in the phloem tissue of the stem, demonstrating slow exchange of Sr with sieve elements or proximal phloem parenchyma and companion cells.
[1]
K. E. Simmons,et al.
Relationship of calcium nutrition to internal brown spot of potato tubers and sub-apical necrosis of sprouts
,
1986,
American Potato Journal.
[2]
B. Shelp.
The Composition of Phloem Exudate and Xylem Sap from Broccoli (Brassica oleracea var. italica) Supplied with NH4+, NO⊟3 or NH4NO3
,
1987
.
[3]
M. Drew,et al.
Radial Movement of Cations across Aerenchymatous Roots of Zea mays Measured by Electron Probe X-Ray Microanalysis
,
1986
.
[4]
P. Millard,et al.
Fractionation and distribution of calcium in sprouting and non-sprouting potato tubers
,
1985
.
[5]
H. Marschner.
General Introduction to the Mineral Nutrition of Plants
,
1983
.
[6]
E. A. Kirkby,et al.
Maximizing calcium uptake by plants
,
1979
.
[7]
J. Raven.
H+ AND Ca2+ IN PHLOEM AND SYMPLAST: RELATION OF RELATIVE IMMOBILITY OF THE IONS TO THE CYTOPLASMIC NATURE OF THE TRANSPORT PATHS
,
1977
.
[8]
H. Ziegler.
Nature of Transported Substances
,
1975
.
[9]
J. Moorby,et al.
The Transport of Sugar, Water, and Ions into Developing Potato Tubers
,
1969
.