What are tree rings? What can be determined by the growth rings? Why are tree rings not visible in many tropical plants?

All layers of wood cells formed in spring, summer and autumn form an annual growth ring. Small autumn cells differ from large spring wood cells of the next year, which are next to them. Therefore, the border between adjacent growth rings on the cross section of wood is clearly visible in many trees. By counting the number of tree rings with a magnifying glass, you can determine the age of a sawn tree or branch cut. Tropical plants constantly live in warm climates; autumn and spring wood cells do not differ in size. Therefore, the boundaries between the growth rings are not visible.