Question

In the current unit, you learned the variation in the types of cells found in xylem and the structural difference in various types of xylem. If you were given a piece of wood, what characteristics would you use to decide whether the wood is from a woody dicotyledon or from a conifer? Explain.

State the characteristics and explain why those characteristics distinguish between woody dicotyledons and conifers.

Answer 1

Characteristics used to decide whether wood is from conifers or woody dicotyledons:

• wood consist of secongary xylem, produced by vascular cambium.
• Distinct growth ring, as growth is cyclic, bordered by small dark cell indicating end of growing season and light cells indicating growth resumption.
• The wood is uniform and simpler is structure than hardwood or woody dicotyledons.
• The conifers wood has tracheid and lesser amount of parenchyma.
• The wood has longitudinal resin canals, which are lined with living cells in duct and rays.
• There are no prominent pores, as observed in woody dicotyledons with vessels.
• The wood is not textured as in woody dicotyledons.

Characteristics of conifer wood		Reasons that distinguishes from woody dicotyledons
Conifers	Woody dicotyledons	Conifers	Woody dicotyledons
Soft wood- gymnosperms	Hardwood - angiosperms	Non-porous- less xylem	Porous and has more xylem
No observable pores.	Prominent pores observed	Contains only tracheid (95%) and no vessels, which transport water and support trunk. Smaller amount of parenchyma present	Contains mixture of: 1. Vessel- dead, lignified, pitted water-conducting elements · 2. Tracheid (5%)- similar to vessels. 3. Parenchyma- living storage cells 4. Fibres—often dead, lignified support cells .
Resin ducts	Only present in some	Resins protect from bacteria and fungi.	Resin-like substances may be present in some, like kino or gum.
Compression wood formed	Tension wood formed	More lignin- underside of branch	More cellulose- upper side of trunk
Not textured.	textured	Lacks texture or are more homogenous- simple with tracheid and no vessels.	More textured- associated with mixture of vessel elements and fibres.