1 wood 280 wood anatomy and identification dr. simon ellis
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WOOD 280
Wood Anatomy and IdentificationDr. Simon Ellis
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Lodgepole pine Hemlock
Douglas-fir Spruce
Softwoods
Aspen Oak
Birch Maple
Hardwoods
(Waddington arboretum)
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May 3 May 21
October 11 December 20
(Ellis)
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*
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Tree trunk showing the successive concentric layers
Outer bark - dead tissue that protects the inner tissues from drying out, from mechanical injury and from insects
Inner bark (phloem) – conducts sugars produced by photosynthesis to the roots and other non-synthetic parts of the tree
Cambium – produces secondary xylem and secondary phloem
Sapwood – consists of xylem tissues through which water and minerals move from the soil to the leaves and other living parts of the tree
Heartwood – composed entirely of dead cells, supporting column of the mature tree
(St. Regis Paper Company)
*Outer bark
SapwoodHeartwood
Cambium
Inner bark
Outer bark
Sapwood
Heartwood
Cambium
Inner bark
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Sapwood - Heartwood
Sapwood Heartwood
(Hoadley) (Core, Côté & Day)
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earlywood latewood
(Hoadley)
9(Haygreen and Bowyer)
Three-dimensional representation of the vascular cambium
(Haygreen and Bowyer)
Cambial cell division
11(Haygreen and Bowyer)
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c cortexd epidermise epidermispc procambiump pithpp primary phloempx primary xylemvc vascular cambiumsp secondary phloemsx secondary xylem
Ontogeny of youngtree stem
(Panshin and de Zeeuw)
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Cell development at apical shoot
Apical initials
Mother cells
Procambium
Protoderm
Ground meristem
Epidermis
Cortex
Pith
Vascular cambium
Primary xylem
Primary phloem
Secondary xylem
Secondary phloem
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Representation of developing stem
(Haygreen and Bowyer)
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1. Mature xylem2. Zone of xylem differentiation3. Cambial zone4. Zone of phloem differentiation5. Mature phloem
Portion of a transverse section of a young stem showing arrangement of tissues
(Zimmerman and Brown)1 2 3 4 5
*
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bark
mature phloem
maturing phloem
differentiating phloem radially enlarging phloem
dividing phloem (phloem mother cells)
cambium cambial initial (dividing)
dividing xylem (xylem mother cells)
differentiating xylem radially enlarging xylem
maturing xylem
mature xylem
pith
Cell types and tissues associated with cambial activity
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Periclinal division of cambial fusiform initials
(Haygreen and Bowyer)
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Anticlinal division of cambial fusiform initials
(Panshin and de Zeeuw)
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Formation of new ray initials in the vascular cambium
(a) (b) (c) (d) (e) (f)(a) Initial a with extensive ray contact survives, while initial b with sparse ray contact matures into a deformed cell and
disappears(b) A ray is split by instrusive growth of a fusiform initial(c) A new ray initial arising from pinching off the top of a fusiform initial(d) Two single ray cells are formed through reduction of a short fusiform initial; either or both of these cells may survive and
later develop into rays consisting of a number of cells formed by subsequent division of these initials or they may be eliminated
(e) A new ray is formed by septation of the entire short fusiform initial(f) A new ray initial is formed on the side of a fusiform initial, which will continue to function as such
(Panshin and de Zeeuw)
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Plant Hormones – nature, occurrence and effects
Hormone Chemical Nature Sites of Biosynthesis Transport Primary Effects
Auxins Indole-3-acetic acid
Apical bud Cell to cell, unidirectional (down)
Apical dominance promotion of cambial activity
Cytokinin Phenyl urea compounds
Roots tips Via xylem from roots to shoots
Cell division, delay of leaf senescence
Gibberellins Gibberellic acid Young tissues of shoot and developing seeds
Via xylem and phloem
Hyperelongation of shoots, induction of seed germination
Ethylene Ethylene Most tissues in response to stress, during senescence or ripening
By diffusion from its site of synthesis
Fruit ripening, leaf and flower senescence
Abscisic acid Synthesized from mevalonic acid
Mature leaves in response to water stress
Via the phloem Stomatal closure, induction of photosynthate transport
(Raven, Evert & Eichorn)
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Plant Growth Hormones