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Understanding Cambial Behaviour The key to wood quality

Understanding Cambial Behaviour The key to wood quality. A brief history Terminology Dormancy and reactivation Growth of derivatives and wall formation Pitting and plasmodesmata. A brief history. Nehemiah Grew (1641-1712). Grew’s drawing of elm (detail). Charles Francois Brisseau-Mirbel.

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Understanding Cambial Behaviour The key to wood quality

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  1. Understanding Cambial Behaviour The key to wood quality

  2. A brief history • Terminology • Dormancy and reactivation • Growth of derivatives and wall formation • Pitting and plasmodesmata

  3. A brief history

  4. Nehemiah Grew (1641-1712)

  5. Grew’s drawing of elm (detail)

  6. Charles Francois Brisseau-Mirbel • Proposed that cambium was a tissue rather than a sap (1808)

  7. Mirbel’s (1827) diagram of elm (from Larson, 1994)

  8. Cambial cell theories • Hartig (1853)- Back to back theory • Phloem initial • Xylem initial

  9. Cambial cell theories • Sanio (1863)- Single initial theory

  10. Cambial cell theories • Raatz/Mischke (1892) – Multiple initial theory

  11. Oblique orientation of plane of division • Kinoplasmic fibres (microtubules) • Kinoplasmosomes (phragmoplast

  12. From Bailey (1923) • Anticlinal pseudotransverse division • Transverse division

  13. Length of cambium/cambial age (from Bailey 1923) • A: Conifer or vessel-less dicot. (12 species) • B: Less specialised dicot. (10 species) • C: Highly specialised dicot. (10 species) • D: Dicot. with storeyed cambium (10 species)

  14. Vacuolation in cambial cells (Bailey 1930)

  15. Pinus radiata Active cambium Nomenclature Cambium? Cambial Zone?

  16. Butterfield (1975) IAWA Bulletin 13 – 14 Cambium “a multiseriate zone of periclinally dividing cells lying between the differentiating secondary xylem and phloem, with a distinct initial capable of both periclinal and anticlinal divisions lying somewhere within each radial file of cells”

  17. Cambium according to Butterfield

  18. Schmid (1976) IAWA Bulletin 51-59 “Cambium” equivalent to the “initiating layer” “Cambium” applied to the entire differentiating region might lead to the conception that the cambium is a multiseriate layer of initials”

  19. Cambium according to Schmid ?

  20. The difficulty of identifying the initial means the terms have been used interchangeably

  21. Pinus radiata Mid-winter A slowly dividing meristem

  22. Pinus radiata Mid-winter Cambium Butterfield Schmid ?

  23. Humpty DumptyFrom “Through the Looking Glass – and what Alice found there” by Lewis Carroll “When I use a word”, Humpty Dumpty said in rather a scornful tone, “it means just what I choose it to mean – neither more nor less”

  24. Can an initial ever be identified with certainty?

  25. Aesculus hippocastanum • February Cells appear similar across the cambium

  26. Identifying an initial Boundary parenchyma phloem side Boundary parenchyma xylem side

  27. A. hippocastanum TEM Boundary parenchyma (phloem side)

  28. A. hippocastanum TEM Phloem cells in suspended or slow development

  29. A. hippocastanum TEM Fusiform Initial

  30. A. hippocastanum TEM Boundary parenchyma xylem side

  31. Sieve element/companion cell pair in a state of arrested development Initial

  32. Boundary parenchyma Companion cell precursor Sieve/element precursor

  33. Phloem boundary cell Previous season’s phloem: Sieve tube member Companion cells 9 February

  34. Dormancy and reactivation

  35. Dormant Cambium Fragmented vacuome

  36. Storage materials in dormant fusiform cells Spherosomes (lipids) Protein bodies “Thick” cell walls

  37. 9 February Fusiform initial Ray initial Starch

  38. Cambial reactivation in Aesculus • Activity can be detected in the cytoplasm of cambial zone cells long before any signs of activity are displayed by the tree.

  39. Active dictyosome in a boundary layer cell of dormant cambium 23 February

  40. Developing and mature coated vesicles • 8 March

  41. Reactivation (16 March) • Expanding phloem precursors • Fusiform initial • Boundary parenchyma

  42. Dividing phloem mother cell (16 March) New tangential wall

  43. 13 April • Boundary parenchyma • Cytoplasm confined to a thin parietal layer • Boundary parenchyma

  44. 23 April • Developing phloem cells • Dividing initial • Xylem mother cell • New xylem elements

  45. Typically in the Reading area, Aesculus bud-break occurs in late March, with leaves fully emerged by late April • Xylem formation appears to begin coincidentally with leaves beginning to export photosynthate

  46. Reactivation sequence • Larson (1994): • Xylem production first – 26 species • Phloem production first – 21 species • Simultaneous production – 10 species

  47. Observations are inconsistent between authors • Acer pseudoplatanus, Quercus rubra , Pinus sylvestris and Vitis vinifera appear in the list of xylem reactivators and phloem reactivators • In the Pinaceae: • Pinus halepensis and rigida are xylem reactivators • Pinusbanksiana, resinosa, and strobus (five authors) are phloem reactivators • Picea excelsa, rubens and rubra are xylem reactivators, • Piceaabies is a phloem reactivator • Picea glauca a simultaneous reactivator.

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