Types of Wood

Vascular cambium

• Vascular cambium is a type of meristem, a lateral meristem to be precise (on the basis of its position). It is made up of actively dividing cells and is responsible for the formation of secondary vascular tissues, i.e. secondary xylem and secondary phloem.
• Vascular cambium forms secondary xylem towards the inner side, which is commonly referred to as wood.

Types of wood

1. Spring wood and Autumn wood / Early wood and Late wood
2. Sapwood and Heartwood / Alburnum and Duramen
3. Softwood and Hardwood / Non-porous and Porous wood

Differences

Spring wood and autumn wood

SPRING WOOD	AUTUMN WOOD
Formed during the spring season	Formed during the autumn season
Formed early in the year, thus called early wood	Formed late in the year, thus called late wood
Lighter in colour	Darker in colour
Rings are much thicker, as the cambium is more active during spring and forms more xylary elements	Rings are relatively narrower, as the vascular cambium is less active during autumn
Vessels have a much wider lumen, as more transpiration occurs during spring	Vessels have a relatively narrow lumen, as transpiration is less during autumn
Lower density	Higher density
The transition from spring wood to autumn wood is slow	The transition from autumn wood to spring wood is fast

Note

• Spring wood and autumn wood rings are not distinct in trees growing in tropical regions, due to almost constant climatic conditions throughout the year.
• Spring wood and autumn wood are absent in roots.
• One ring of spring wood + one ring of autumn wood = one annual ring.
• Dendrochronology – estimating the age of trees by counting the number of annual rings.

Sapwood and heartwood

SAPWOOD	HEARTWOOD
Also known as alburnum	Also known as duramen
Peripheral part of the wood	Central part of the wood
Lighter in colour	Darker in colour
Soft and not very durable, due to the presence of living cells	Hard and very durable, due to various depositions and the absence of living cells
The lumen of the vessels is unblocked, as tyloses are not formed	The lumen of the vessels is blocked by extensions of xylem parenchyma into the vessel lumen, called tyloses or tracheal plugs
Function: conduction of sap	Function: provides mechanical strength and microbial resistance

Softwood and hardwood

SOFTWOOD	HARDWOOD
Formed in gymnosperms	Formed in angiosperms
Tracheids and xylem parenchyma are present, but vessels and xylem fibres are absent	All 4 xylary elements, i.e. tracheids, vessels, xylem fibres and xylem parenchyma, are present
Contains more living cells and is soft	Contains more dead cells and thus is hard
Also known as non-porous wood, due to the absence of vessels	Also known as porous wood, due to the presence of vessels
Also known as homoxylous wood, as only one type of conducting element, i.e. tracheids, is present	Also known as heteroxylous wood, as two types of conducting elements, i.e. tracheids and vessels, are present

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