The bulk of the stem of the gymnosperms and dicotyledonous plants is formed by the wood, which is a complex secondary tissue. These are the main products of the metabolism of trees. “Wood” term is applicable to the secondary xylem, which is formed by the vascular cambium at the time of secondary growth.
Traits of Wood
Attributes of wood are based on the tissue components. Such features help recognize the wood. Some features are –
- Spring and autumn
- Alburnum (sapwood) and Duramen (heartwood)
- Softwood (porous wood) and hardwood (non-porous wood)
Spring Wood and Autumn Wood
The action of cambium in temperate perennial plants begins in the spring. During this period, the wood produced is the spring wood or early wood. The cells of wood which are produced at later parts of the growth season are autumn wood or summer or late wood.
Early wood or Spring wood
Environmental conditions have a sharp impact on the formation of the secondary xylem. During favourable conditions, i.e., at the time of summer and spring, the cambium is active producing ample amounts of wood. Here, the wood has a light colour comprising wider and larger xylem elements. It is referred to as early or spring wood.
Late wood or Autumn Wood
The cambium is less active at the time of autumn and winter producing lesser quantities of wood. Such a wood is darker in appearance and comprises narrow and small xylem components with relatively thicker walls. Such a cambium is referred to as late wood or autumn wood.
Both the spring wood and the autumn wood produced in one year together form a ring which is referred to as annual ring or growth rings. The transformation of spring wood to autumn wood which constitutes an annual ring is progressive, however, the transition to spring wood from autumn wood of the following year is abrupt and sudden. Consequently, every year, the growth is discrete.
The approximate age of the plant can be determined by the number of annual rings present. As a matter of fact, the science of determining the age of the tree by taking into account the number of annual rings is referred to as dendrochronology.
Most shrubs and trees of the temperate origins depict distinct growth layers referred to as growth rings or the annual rings of the secondary xylem. These rings seem as concentric rings observed in the transverse sections of the stem, wherein each of these rings indicate a growth of secondary xylem for one year. Such rings are formed at the straight parts of the stem given appropriate conditions, while the eccentric rings emerge due to unfavourable natural disasters.
Hence, the action of the cambium is a seasonal process. The quiescence and the periodic activity of the cambium results in the formation of the growth rings or the annual rings, which are distinct as there is a structural difference. The difference also lies in the colors they show between the secondary xylem that takes form during the late and early parts of the growth season.
How is Spring Wood Different From Autumn Wood?
Spring wood differs from autumn wood in several ways, they are –
|Attributes||Spring Wood||Autumn Wood|
|Season of formation||Spring||Autumn|
|Colour of the wood||Light||Dark|
|Constituency in annual ring||Major part||Forms a narrow strip|
|Also known as||Early wood||Late wood|
|Position in annual ring||Towards the beginning||Towards the end|
|Quantity of xylem fibers||A few||Ample|
|Nature of cavities of xylem vessels||Wider cavities||Narrow cavities|
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