Tree Architecture and

Growth

Part 2

Secondary Growth

• Cambium

• Wood (Xylem)

• Phloem

• Stem and branches

Cambium

• Cambial meristem

• Xylem

– To the inside

• Phloem

– To the outside

Xylem and Phloem

• Xylem

– Wood

– Water transport

– Mass transport

• Phloem

– Chemical transport

– Source – sink

– Active loading

Xylem

• Tracheids

– Gymnosperms

• Vessels

– angiosperms

Conifer WoodPiece of conifer wood with

four annual rings.

Meaning of the letters:TR = transverse sectionR = radial sectionTA = tangential section

B = barkAR = annual ringE = early woodL = late wood

c = cambiumr = rayrd = resin duct

After Strasburger (1967): Lehrbuch der Botanik

Conifer wood

After T.L. Rost et al (1979): Botany, a brief introduction to plant biology.

Black walnut (Fred Sutherland)

Early wood – Late wood

• Early wood– Laid down first

– Lighter

– Less dense

• Late wood– Laid down later

– darker in color

– denser

• Juvenile wood

– Wood formed under the influence of the apical meristem in the live crown

• Mature Wood

– Wood formed lower down the stem where the influence of the live crown is much less

• Juvenile-mature wood distinction is completely different from heartwood-sapwood distinction.

• Juvenile wood is formed throughout the life of the tree not just in young trees.

BC Ministry of Forests - Research Branch - Forest Productivity Section

Reaction wood

• Hardwoods

– Tension wood

• Conifers

– Compression wood

Compression wood

Compression Wood

Compression Wood

Callous Wood

• Formed after an injury

– Fire scars

Ring Widths

• Crossectional area

• Matter of geometry

• Distance from crown

• Mechanical stimulation

RR’

Area of old tree (radius=A) = A2

Area of new tree (radius=R) = (A+B)2

Ring (new growth) = (A+B)2 - A2

A B A’ B’

If new wood = 75

If tree had diameter of 5 then ring width = 5

If tree had diameter of 11 then ring width = 3

Stem Form

Ring Area

Stem Form

Ring Width

Priorities for Photosynthate

1. Respiration

2. Foliage – Fine Roots

3. {Reproduction}

4. Primary Growth

5. Secondary Growth –Secondary Compounds

• Incomplete rings

• Cambial mortality

• False rings

Taper

Knots

• Live knots

• Dead knots

Live Knots – Dead Knots

Stem Quality Considerations

• Straightness

• Ring characteristics

• Density

• Knots