Question

Answer the following question.

There were two cut logs of wood lying in the campus. One had growth rings and other didn’t. Teacher said it is due to differences in their pattern of growth which is dependent on the season. How?

Answer 1

1. It is possible that one of the cut logs was of a tropical tree, whereas the other was of a temperate tree. Since tropical trees grow in a similar manner all year, growth rings are not apparent. Another explanation for this could be that the log which had growth rings must be of an old tree which has experience many seasons, whereas the log without growth rings must be of younger tree, that has not been subjected to seasonal changes and hence not developed prominent growth rings.
2. Growth rings are formed due to cambial activity during favourable and non-favourable climatic conditions.
3. During favourable conditions, spring wood (early wood) is formed which has broader xylem bands, lighter colour, tracheids with thin wall and wide lumen, fibres are less in number, low density. Whereas, during unfavourable conditions, autumn wood (late wood) is formed which has narrow xylem band, darker in colour, a lumen is narrow and walls are thick with abundant fibres, high density.
4. Spring wood and autumn wood that appears as alternate light and dark concentric rings, constitute an annual ring or growth ring.
5. These growth rings can be used to estimate the age of the tree. These are found more in older trees as compare to a younger tree.