From compartmental analysis of radioisotope elution measurements, concentrations and fluxes of Mg2+ were estimated for cortical cells in root segments of onion, Allium cepa L., relative to a complete nutrient solution containing 0.25 mM Mg2+. Five compartments for Mg2+ in the cortex were found and, in order of increasing rates of exchange, identified with the vacuoles and the cytoplasm of the cortical parenchyma, the Donnan free space, the water free space, and the superficial film of solution on the segments. With the Ussing-Teorell flux ratio equation as the criterion, it was concluded that Mg2+ entered the cytoplasm passively and was actively pumped back across the plasmalemma. Mg2+ concentration in the vacuole could be estimated only as lying between wide limits (1.3 to 14.3 μeq ml-1), but whatever the concentration within this range, it was concluded that Mg2+ was passively distributed across the tonoplast. Net flux was zero and the vacuolar concentration commensurate with this was found to be 6.6 μeq ml-1. The transported fraction of total efflux, appearing at the segment cut ends, was estimated separately. Magnesium was found to be transported almost exclusively in the basipetal direction.
This is a preview of subscription content, log in to check access.
Buy single article
Instant access to the full article PDF.
Price includes VAT for USA
Subscribe to journal
Immediate online access to all issues from 2019. Subscription will auto renew annually.
This is the net price. Taxes to be calculated in checkout.
Allen, R.D., Jacobsen, L., Joaquin, A., Jaffe, L.F.: Ionic concentrations in developing Pelvetia eggs. Develop. Biol. 27, 538–545 (1972)
Bowling, D>J.F., Macklon, A.E.S., Spanswick, R.M.: Active and passive transport of the major nutrient ions across the root of Ricinus communis. J. exp. Bot. 17, 410–416 (1966)
Higinbotham, N., Etherton, B., Foster, R.J.: Mineral ion contents and cell transmembrane electropotentials of pea and oat seedling tissue. Plant Physiol. 42, 37–46 (1967)
Kaplan, O.B.: Kinetics of magnesium absorption by excised barley roots. Dissertation, Univ. of California, Davis, 130 pp.Diss. Abstr. Int. B., 1970, 30, 3929 (1969)
Lazaroff, N., Pitman, M.G.: Calcium and magnesium uptake by barley seedlings. Aust. J. biol. Sci. 19, 991–1005 (1966)
Leggett, J.E., Gilbert, W.A.: Magnesium uptake by soybeans. Plant Physiol. 44, 1182–1186 (1969)
Maas, E.V., Ogata, G.: Absorption of magnesium and chloride by excised corn roots. Plant Physiol. 47, 357–360 (1971)
Macklon, A.E.S.: Cortical cell fluxes and transport to the stele in excised root segments of Allium cepa L. I. Potassium, sodium and chloride. Planta (Berl.) 122, 109–130 (1975a)
Macklon, A.E.S.: Cortical cell fluxes and transport to the stele in excised root segments of Allium cepa L. II. Calcium. Planta (Berl.) 122, 131–141 (1975b)
Moore, D.P., Oberstreet, R., Jacobson, L.: Uptake of magnesium and its interaction with calcium in excised barley roots. Plant Physiol. 36, 290–295 (1961)
Pitman M.G., Lüttge, U., Kramer, D., Ball, E.: Free-space characteristics of barley leaf slices. Aust. J. Plant Physiol. 1, 65–75 (1974)
Weisenseel, M.H., Jaffe, L.F.: Membrane potential and impedance of developing fucoid eggs. Develop. Biol. 27, 555–574 (1972)
About this article
Cite this article
Macklon, A.E.S., Sim, A. Cortical cell fluxes and transport to the stele in excised root segments of Allium cepa L.. Planta 128, 5–9 (1976). https://doi.org/10.1007/BF00397171
- Cortical Cell
- Ratio Equation
- Root Segment
- Flux Ratio
- Allium Cepa