Planta

, Volume 192, Issue 2, pp 239–248 | Cite as

Phloem transport and differential unloading in pea seedlings after source and sink manipulations

  • Alexander Schulz
Article

Abstract

Phloem transport was investigated in pea seedlings after application of [14C]sucrose to the cotyledons. The accumulation of the label in segments of young seedlings shows a differential unloading along the plant axis. Shoot and root exhibit tip-to-base gradients of sink strength. In the primary root, the sink-strength profiles reflect not only the importance of the apical meristem, but show also the starting points of cambial activity and production of secondary vascular elements. Experiments including partial removal of the source and manipulations of the sink strength indicate that translocation of pea seedlings is sink-regulated and responds rapidly to changed apoplastic conditions in the apical root region. Here, a lowered water potential leads to an increase of phloem unloading that is suggested to supply the assimilate demand for the short-term osmoregulation of affected cells via the symplasmic pathway.

Key words

Osmoregulation Phloem transport Phloem unloading Pisum Sink strength Source/sink relations 

Abbreviation

PCMBS

parachloromercuribenzenesulfonic acid

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References

  1. Baker, D.A., Milburn, J.A., eds. (1989) Transport of photoassimilates Longman, Scientific & Technical, Harlow, UKGoogle Scholar
  2. Canny, M.J. (1973) Phloem translocation. Cambridge University PressGoogle Scholar
  3. Delrot, S., Despeghel, J.-P., Bonnemain, J.-L. (1980) Phloem loading inVicia faba leaves: Effect of N-ethylmaleimide and parachloromercuribenzenesulfonic acid on H+ extrusion, K+ and sucrose uptake. Planta149, 144–148Google Scholar
  4. Dick, P.S., ap Rees, T. (1975) The pathway of sugar transport in roots ofPisum sativum. J. Exp. Bot.26, 305–314Google Scholar
  5. Enstone, D.E., Peterson, C.A. (1992) The apoplastic permeability of root apices. Can. J. Bot.70, 1502–1512Google Scholar
  6. Erwee, M.G., Goodwin, P.B. (1984) Characterization of theEgeria densa Planch, leaf symplast: Response to plasmolysis, deplasmolysis and to aromatic amino acids. Protoplasma122, 162–168Google Scholar
  7. Eschrich, W. (1989) Phloem unloading of photoassimilates. In: Transport of photoassimilates, pp. 206–263, Baker, D.A., Milburn, J.A., eds. Longman Scientific & Technical, Harlow, UKGoogle Scholar
  8. Farrar, J.F. (1985) Fluxes of carbon in roots of barley plants. New Phytol.99, 57–69Google Scholar
  9. Farrar, J.F., Minchin, P.E.H. (1991) Carbon partitioning in split root systems of barley — relation to metabolism. J. Exp. Bot.42, 1261–1269Google Scholar
  10. Geiger, D.R., Fondy, B.R. (1980) Response of phloem loading and export to rapid changes in sink demand. Ber. Dtsch. Bot. Ges.93, 177–186Google Scholar
  11. Grimm, E., Bernhardt, G., Rothe, K., Jacob, F. (1990) Mechanism of sucrose retrieval along the phloem path — a kinetic approach. Planta182, 480–485Google Scholar
  12. Heyser, W, Heyser, R., Eschrich, W., Leonard, O.A. (1976) The influence of externally applied organic substances on phloem translocation in detached maize leaves. Planta132, 269–277Google Scholar
  13. Ho, L.C., Grange, R.I., Shaw, A.F. (1989) Source/sink regulation. In: Transport of photoassimilates, pp. 306–343, Baker, D.A., Miburn, J.A., eds. Longman Scientific & Technical, Harlow, UKGoogle Scholar
  14. Itoh, K., Nakahara, K., Ishikawa, H., Ohta, E. Sakata, M. (1987a) Osmostic adjustment and osmotic constituents in roots of mung bean seedlings. Plant Cell Physiol.28, 397–403Google Scholar
  15. Itoh, K., Nakamura, Y, Kawata, H., Yamada, T., Ohta, E., Sakata, M. (1987b) Effect of osmotic stress on turgor pressure in mung bean root cells. Plant Cell Physiol.28, 987–994Google Scholar
  16. Kallarackal, J., Orlich, G., Schobert, C., Komor, E. (1989) Sucrose transport into the phloem ofRicinus communis L. seedlings as measured by the analysis of sieve-tube sap. Planta177, 327–335Google Scholar
  17. Kochian, L.V., Lucas, W.J. (1983) Potassium transport in corn roots. II. The significance of the root periphery. Plant Physiol.73, 208–215Google Scholar
  18. Lambers, H. (1988) Growth, respiration, exudation and symbiotic associations: the fate of carbon translocated to the roots. In: Root development and function (Soc. Exp. Biol. Seminar Series vol. 30), pp. 125–145, Gregory, P.J., Lake, J.V., Rose, D.A., eds. CambridgeGoogle Scholar
  19. Lambers, H., van der Werf, A., Konnings, H. (1991) Respiratory patterns in roots in relation to their functioning. In: Plant roots: the hidden half, pp. 229–263, Waisel, Y., Eshel, A., Kafkafi, U., eds. Marcel Dekker, New York Basel Hong KongGoogle Scholar
  20. Lee-Stadelmann, O.Y, Stadelmann, E.J. (1989) Plasmolysis and deplasmolysis. Methods Enzymol.174, 225–246Google Scholar
  21. M'Batchi, B., Delrot, S. (1984) Parachloromercuribenzenesulfonic Acid. A potential tool for differential labeling of the sucrose transporter. Plant Physiol.75, 154–160Google Scholar
  22. Meshcheryakov, A., Steudle, E., Komor, E. (1992) Gradients of turgor, osmotic pressure, and water potential in the cortex of the hypocotyl of growingRicinus seedlings. Plant Physiol.98, 840–852Google Scholar
  23. Milburn, J.A., Kallarackal, J. (1989) Physiological aspects of phloem translocation. In: Transport of photoassimilates, pp. 264–305, Baker, D.A., Milburn, J.A., eds. Longman Scientific & Technical, HarlowGoogle Scholar
  24. Minchin, P.E.H. (1979) The relationship between spatial and temporal tracer profiles in transport studies. J. Exp. Bot.30, 1171–1178Google Scholar
  25. Morrod, R.S. (1974) A new method for measuring the permeability of plant cell membranes using epidermis free leaf disks. J. Exp. Bot.25, 521–533Google Scholar
  26. Murphy, R. (1989) Water flow across the sieve tube boundary: estimating turgor and some implications for phloem loading and unloading. IV. Root tips and seed coats. Ann. Bot.63, 571–579Google Scholar
  27. Oparka, K.J., Prior, D.A.M. (1992) Direct evidence for pressure-generated closure of plasmodesmata. Plant J.2, 741–750Google Scholar
  28. Oparka, K.J., Wright, K.M. (1988) Influence of cell turgor on sucrose partitioning in potato tuber storage tissues. Planta175, 520–526Google Scholar
  29. Patrick, J.W. (1990) Sieve element unloading: cellular pathway, mechanism and control. Physiol. Plant.78, 298–308Google Scholar
  30. Schmalstig, J.G., Cosgrove, D.J. (1990) Coupling of solute transport and cell expansion in pea stems. Plant Physiol.94, 1625–1633PubMedGoogle Scholar
  31. Schulz, A. (1986) Wound phloem in transition to bundle phloem in primary roots ofPisum sativum L. I. Development of bundle-leaving wound-sieve tubes. Protoplasma130, 12–26Google Scholar
  32. Schulz, A., Gersani, M. (1990) Regeneration of sucrose translocation in wounded roots of pea seedlings. J. Plant Physiol.136, 599–605Google Scholar
  33. Sharp, R.E., Silk, W.K., Hsiao, T.C. (1988) Growth of the maize primary root at low water potentials. Plant Physiol.87, 50–57Google Scholar
  34. Sharp, R.E., Hsiao, T.C., Silk, WK. (1990) Growth of the maize root at low water potentials. II. Role of growth and deposition of hexose and potassium in osmotic adjustment. Plant Physiol.93, 1337–1346Google Scholar
  35. Spollen, W.G., Sharp, R.E. (1991) Spatial distribution of turgor and root growth at low water potentials. Plant Physiol.96, 438–443Google Scholar
  36. Steudle, A. (1992) The biophysics of plant water: compartmentation, coupling with metabolic processes, and flow of water in plant roots. In: Water and life, pp. 173–203, Somero, G.N., Osmond, C.B., Bolis, C.L., eds. Springer, Berlin HeidelbergGoogle Scholar
  37. Torrey, J.G. (1965) Physiological bases of organization and development in the root. In: Handbuch der Pflanzenphysiologie, vol. XV, part 1: Differenzierung und Entwicklung, pp. 1256–1327, Ruhland, W., ed. Springer Verlag, Berlin Heidelberg New YorkGoogle Scholar
  38. Wanner, H. (1950) Histologische und physiologische Gradienten in der Wurzelspitze. Ber. Schweiz. Botan. Gesellsch.60, 404–412Google Scholar
  39. Warmbrodt, R.D. (1987) Solute concentrations in the phloem and apex of the root ofZea mays. Am. J. Bot.74, 394–402Google Scholar
  40. Westgate, M.E., Boyer, J.S. (1985) Osmotic adjustment and the inhibition of leaf, root, stem and silk growth at low water potentials in maize. Planta164, 540–549Google Scholar
  41. Willenbrink, J., Doll, S., Getz, H.-P., Meyer, S. (1984) Zuckeraufnahme in isolierten Vakuolen und Protoplasten aus dem Speichergewebe von Beta-Rüben. Ber. Deutsch. Bot. Ges.97, 27–39Google Scholar
  42. Williams, J.H.H., Minchin, P.E.H., Farrar, J.F. (1991) Carbon partitioning in split root systems of barley: The effects of osmotica. J. Exp. Bot.42, 453–460Google Scholar

Copyright information

© Springer-Verlag 1994

Authors and Affiliations

  • Alexander Schulz
    • 1
  1. 1.Botanisches Institut der UniversitätKielGermany

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