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The development of phloem anastomoses between vascular bundles and their role in xylem regeneration after wounding in Cucurbita and Dahlia


The differentiation of phloem anastomoses linking the longitudinal vascular bundles has been studied in stem internodes of Cucurbita maxima Duchesne, C. pepo L. and Dahlia pinnata Cav. These anastomoses comprise naturally occurring regenerative sieve tubes which redifferentiate from interfascicular parenchyma cells in the young internodes. In all three species, severing a vascular bundle in a young internode resulted in regeneration of xylem to form a curved by-pass immediately around the wound. The numerous phloem anastomoses in these young internodes were not involved in this process, the regenerated vessels originating from interfascicular parenchyma alone. Conversely, in mature internodes of Dahlia, the regenerated vessels originated from initials of the interfascicular cambia, and their phloem anastomoses did not influence the pattern of xylogenesis. On the other hand, in old internodes of Cucurbita, in which an interfascicular cambium was not yet developed, the parenchyma cells between the bundles had lost the ability to redifferentiate into vessel elements, and instead, regenerated vessels were produced in the phloem anastomoses. Thus, the wounded region of the vascular bundle was not bypassed via the shortest, curved pathway, but by more circuitous routes further away from the wound. Some of the regenerated vessels produced in the phloem anastomoses were extremely wide, and presumably efficient conductors of water. It is proposed that the dense network of phloem anastomoses developed during evolution as a mechanism of adaptation to possible damage in mature internodes by providing flexible alternative pathways for efficient xylem regeneration in plants with limited or no interfascicular cambium.

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  1. Aloni R (1980) Role of auxin and sucrose in the differentiation of sieve and tracheary elements in plant tissue cultures. Planta 150: 255–263

  2. Aloni R (1987a) The induction of vascular tissues by auxin. In: Davis PJ (ed) Plant hormones and their role in plant growth and development. Martinus Nijhoff, Dordrecht Boston, pp 363–374

  3. Aloni R (1987b) Differentiation of vascular tissues. Annu Rev Plant Physiol 38: 179–204

  4. Aloni R (1995) The induction of vascular tissues by auxin and cytokinin. In: Davis PJ (ed) Plant hormones: physiology, biochemistry and molecular biology. 2nd edn. Kluwer Academic Publishers, Dordrecht, London, pp 531–546

  5. Aloni R, Peterson CA (1990) The functional significance of phloem anastomoses in stems of Dahlia pinnata Cav. Planta 182: 583–590

  6. Aloni R, Plotkin T (1985) Wound-induced and naturally occurring regenerative differentiation of xylem in Zea mays L. Planta 163: 126–132

  7. Aloni R, Sachs T (1973) The three-dimensional structure of primary phloem systems. Planta 113: 345–353

  8. Aloni R, Zimmermann MH (1983) The control of vessel size and density along the plant axis —a new hypothesis. Differentiation 24: 203–208

  9. Aloni R, Pradel KS, Ullrich CI (1995) The three-dimensional structure of vascular tissues in Agrobacterium tumefaciens-induced crown galls and in the host stems of Ricinus communis L. Planta 196: 597–605

  10. Baum SF, Aloni R, Peterson CA (1991) The role of cytokinin in vessel regeneration in wounded Coleus internodes. Ann Bot 67: 543–548

  11. Esau K (1965) Vascular differentiation in plants. Holt Rinehart Winston, New York

  12. Esau K (1969) The phloem. In: Zimmermann W, Ozenda P, Wulff HD (eds) Encyclopedia of plant anatomy, vol 5, pt 2. Gebruder Borntraeger, Berlin

  13. Fahn A (1990) Plant anatomy. 4th edn. Pergamon Press, Oxford New York

  14. Jacobs WP (1952) The role of auxin in differentiation of xylem around a wound. Am J Bot 39: 301–308

  15. Kaan Albert A von (1934) Anatomische und physiologische Untersuchungen über die Entstehung von Siebröhrenverbindungen. Z Bot 27: 1–92

  16. Mauseth JD (1988) Plant anatomy. Benjamin/Cummings, Menlo Park California

  17. Moore R, Clark WD, Stern KR, Vodopich D (1995) Botany. Brown Publishers, Dubuque Iowa

  18. Raven PH, Evert RF, Eichhorn SE (1992) Biology of plants. 5th edn. Worth Publishers, New York

  19. Roberts LW, Gahan PB, Aloni R (1988) Vascular differentiation and plant growth regulators. Springer-Verlag, Berlin Heidelberg New York

  20. Sachs T (1969) Polarity and the induction of organised vascular tissues. Ann Bot 33: 263–275

  21. Sachs T (1981) The control of the patterned differentiation of vascular tissues. Adv Bot Res 9: 151–262

  22. Sachs T (1986) Cellular patterns determined by polar transport. In: Bopp M (ed) Plant growth substances. Springer-Verlag, Berlin Heidelberg, pp 231–235

  23. Zimmermann MH (1983) Xylem structure and the ascent of sap. Springer-Verlag, Berlin Heidelberg New York

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Author information

Correspondence to Roni Aloni.

Additional information

This paper is dedicated to the memory of the late Isaac Blachmann (deceased 19 November 1995), father-in-law of the senior author, for encouragement and advice throughout the years

This research was supported by an International Scientific Exchange Award to R.A. from the Israel Academy of Sciences and The Royal Society.

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Aloni, R., Barnett, J.R. The development of phloem anastomoses between vascular bundles and their role in xylem regeneration after wounding in Cucurbita and Dahlia . Planta 198, 595–603 (1996).

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Key words

  • Cucurbita
  • Dahlia
  • Phloem (anastomoses, development, function)
  • Xylem (regeneration, efficiency)