Forestry 280: Hardwood Anatomy 1

Hardwood Anatomical Structure

• Longitudinal Cells

• Ray Tissue

• Distinction from Softwood anatomy

• Identifying characteristics

Forestry 280: Hardwood Anatomy 2

Longitudinal Cells

• Fibers

• Vessel Elements

•Longitudinal Parenchyma

• Tracheids

Forestry 280: Hardwood Anatomy 3

Fibers

Fiber Tracheids – long, tapered, thick walled hardwood xylem cells

Similar to Softwood Tracheids:

• Contain bordered pits• Secondary thickening of cell wall

Forestry 280: Hardwood Anatomy 4

Fibers

Distinction from Softwood Tracheids:

• Shorter in length, 1 – 2 mm• Round in cross section • Almost solely responsible for strength

Libriform fibers – Similar to fiber tracheidsexcept for “apparent simple pits”

Forestry 280: Hardwood Anatomy 5

Vessel Elements

Vessel Elements – Specialized vertical conducting cells

• Much larger in diameter than other longitudinal hardwood cells

• When viewed in cross section commonly termed pores

• Typically they do not elongate

• These cells join vertically to form vessels

• Vessels often stray from straight alignment

Forestry 280: Hardwood Anatomy 6

Vessel Elements

Wide range of pore diameters 20 – 300 µm

Variation often occurs within a growth ring:

Ring Porous – Early wood contains large vessels late wood with smaller pores

Diffuse Porous – Fairly uniform pore diameter throughout growth rings

Semi–ring–porous or semi–diffuse–porous

Forestry 280: Hardwood Anatomy 7

Vessel Elements

Perforation Plates: Cell divisions that contain unrestricted voids or perforations that allow fluid transport

Perforations formed by enzymatic degradation of plates uponmaturation of the cells

Perforation plate patterns canbe use for species identification purposes

Forestry 280: Hardwood Anatomy 8

Vessel Elements

Vessel Pitting:

Vessel to Vessel – Three typical arrangements (below)

Vessel to fibers or tracheids – Typically bordered

Vessels to parenchyma – Bordered, half-bordered, or simple

Forestry 280: Hardwood Anatomy 9

Vessel Elements

Tyloses: Outgrowths (or ingrowths!)of parenchyma cell walls into the lumenof adjacent vessel elements

Function: Primarily in damaged tissue

• Protect against moisture loss

• Prevent the spread of pathogens

• Act as a barrier in the formation of heartwood

Forestry 280: Hardwood Anatomy 10

Vessel Elements

Tyloses formation:

Enzymatic degradation of pit membranes between parenchyma and vessel elements

Outgrowth of parenchyma cell membrane into vessel (Tylosis)

Tyloses may remain thin walled or experience secondary thickening

Presence of tyloses can affect the utilization of wood

Forestry 280: Hardwood Anatomy 11

Longitudinal Parenchyma

Parenchyma are thin-walled storage cells

May have darkly-stained contents May comprise 1-24% of wood volume

(domestic hardwoods); may be up to 50% (some tropical species)

Forestry 280: Hardwood Anatomy 12

Longitudinal Parenchyma

Axial strand parenchyma – formed by transverse division of fusiform cambial initial

Fusiform parenchyma – derived from fusiform cambial initial tapered at both ends, storied

arrangement

Epithelial cells – surround gum canals or gum ducts, typically traumatic in origin

Forestry 280: Hardwood Anatomy 13

Longitudinal Parenchyma

Parenchyma Arrangement:

Forestry 280: Hardwood Anatomy 14

Hardwood Rays

Cell Types – Ray Parenchyma

Procumbent – horizontally oriented when viewed in radial plane• procumbent = “lying down”• rectangular cells in brick-like arrangement• typically found at the center of rays

Upright – vertically oriented when viewed in radial plane• sometimes called square ray cells• long axis of cell aligned vertically

Forestry 280: Hardwood Anatomy 15

Hardwood Rays

Ray types:

Homocellular – composed of a singlecell type; either procumbent or upright

Heterocellular – composed of both procumbentand upright ray parenchyma cells**************Rays may be narrow (uniseriate), multiseriate,wide “oak-type” (very wide multiseriate rays)or aggregate