Due to differential seasonal activity of cambium,alternate light & dense wood is cut off leading to formation of annual rings.

Formation of Annual Rings in Trees
- Annual rings are formed in trees due to the activity of the cambium layer, a thin layer of meristematic tissue located between the xylem and phloem.
- The cambium is responsible for secondary growth in trees, producing new xylem cells towards the center of the tree and new phloem cells towards the outside.
- During the growing season, the cambium cells divide rapidly, leading to the formation of large, thin-walled cells that make up the spring wood.
- As the season progresses and growth slows down, the cambium produces smaller, thick-walled cells that make up the summer wood.
- The contrast in cell size and density between spring wood and summer wood results in the formation of annual rings in trees.

Growth Rings in Trees
- Growth rings, also known as tree rings, are the concentric circles visible in the cross-section of a tree trunk.
- Each ring represents one year of growth in the life of the tree.
- The width of each ring is determined by factors such as climate, soil conditions, and tree age.
- In favorable growing conditions, trees produce wider rings, while in less favorable conditions, the rings are narrower.
- By analyzing growth rings, scientists can study past climate patterns, tree growth rates, and environmental changes over time.

Conclusion
- In conclusion, annual rings and growth rings in trees are primarily formed due to the activity of the cambium layer.
- The cambium's role in producing xylem and phloem cells during the growing season leads to the formation of distinct annual rings, while the cumulative effect of these rings results in the visible growth rings seen in tree trunks.