Question

Annual rings are distinct in plants growing in
A. Tropical regions
B. Arctic regions
C. Grasslands
D. Temperate regions

Answer 1

Hint: Annual rings are the alternate concentric dark and light rings that consist of autumn wood and spring wood. The darker rings are due to the presence of autumn wood while lighter rings are due to the presence of spring wood.

Complete Answer:
- The vascular cambium that comprises xylem and phloem mainly forms the cambium ring that is actively present in stem and performs the function to cut off new cells both towards the outer side as well as inner sides.
- The cambial ring activity is under the control of many physiological and environmental factors. In temperate regions, the climatic conditions are not uniform throughout the year and vary from time to time.
- In the spring season, the cambium is very active and produces large amounts of xylary elements having vessels with wider cavities. Thus the wood produced during this season is called spring wood or early wood.
- In the autumn season, the cambium is less active and forms fewer xylary elements that have narrow cavities. Thus the wood produced during this season is called autumn wood or late wood.

The correct option is D i.e. temperate regions.

Note: The branch that deals with the study of annual rings for the estimation of age of plants is called dendrochronology. This is usually done by the help of radioactive carbon dating.
- Annual rings are also used for the dendroclimatology (i.e. the branch of science of determining the past climates from tree’s annual rings.
- Annual rings is also useful for determining the time at which wooden buildings are constructed by the help of dendrochronology.