WOOD 280 Wood Anatomy and Identification Dr Simon

WOOD 280 Wood Anatomy and Identification Dr. Simon Ellis 1

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

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

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

Outer bark Inner bark Cambium Sapwood Heartwood

Sapwood - Heartwood Sapwood (Hoadley) Heartwood (Core, Côté & Day) 7

earlywood latewood (Hoadley) 8

(Haygreen and Bowyer) 9

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

Cambial cell division (Haygreen and Bowyer) 11

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

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

Representation of developing stem (Haygreen and Bowyer) 14

Portion of a transverse section of a young stem showing arrangement of tissues * 1. 2. 3. 4. 5. 1 2 3 4 5 Mature xylem Zone of xylem differentiation Cambial zone Zone of phloem differentiation Mature phloem (Zimmerman and Brown) 15

Cell types and tissues associated with cambial activity 16

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

Anticlinal division of cambial fusiform initials (Panshin and de Zeeuw) 18

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) 19

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 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) 20

Plant Growth Hormones 21