1. WOOD 280 – Tree growth and wood formation

2. Softwoods Hardwoods (gymnosperms) (angiosperms)
Lodgepole pine
Hemlock
Aspen
Oak
Douglas-fir
Spruce
Birch
Maple
(Waddington arboretum)

3. May 3
May 21
October 11
December 20
(Ellis)

4. *

5. * Tree trunk showing the successive concentric layers Outer bark
Sapwood
Heartwood
Cambium
Inner bark
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)

6. Sapwood - Heartwood Sapwood Heartwood Sapwood Heartwood (Hoadley)
(r.fld.czu.cz)

7. earlywood
latewood
(Hoadley)

8. (Haygreen and Bowyer)

9. Three-dimensional representation of the vascular cambium
(Haygreen and Bowyer)

10. Cambial cell division
Fusiform initials

11. Apical vs. Lateral Meristems

12. * Ontogeny of young tree stem c cortex d epidermis e endodermisvc
Ontogeny of young tree stem
c cortex
d epidermis
e endodermis
pc procambium
p pith
pp primary phloem
px primary xylem
vc vascular cambium
sp secondary phloem
sx secondary xylem
(Panshin and de Zeeuw)

13. Cell development at apical shoot
Protoderm
Epidermis
Primary phloem
Secondary phloem
Apical initials
Mother cells
Vascular cambium
Procambium
Primary xylem
Secondary xylem
Cortex
Ground meristem
Pith

14. Representation of developing stem
(Haygreen and Bowyer)

15. *
Portion of a transverse section of a young stem showing arrangement of tissues
(Zimmerman and Brown)
Mature xylem
Zone of xylem differentiation
Cambial zone
Zone of phloem differentiation
Mature phloem

16. Cell types and tissues associated with cambial activity

17. Periclinal division of cambial fusiform initials
(Haygreen and Bowyer)

18. Softwood – longitudinal section (tangential)
Longitudinal parenchyma
Ray
Longitudinal tracheids

19. Anticlinal division of cambial fusiform initials
(Panshin and de Zeeuw)

20. 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
A ray is split by instrusive growth of a fusiform initial
A new ray initial arising from pinching off the top of a fusiform initial
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
A new ray is formed by septation of the entire short fusiform initial
A new ray initial is formed on the side of a fusiform initial, which will continue to function as such
(Panshin and de Zeeuw)

21. Plant Hormones – nature, occurrence and effects
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
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)

22. Plant Growth Hormones