Question

Annual rings are seen in temperate zone trees because

• A. Xylem cell size varies with season
• B. Heart wood cells alternate with sap wood cells
• C. Xylem activity varies with season
• D. Resin is deposited in the rings in the stem

Answer 1

The correct option is A Xylem cell size varies with season

In the spring season, cambium is very active and produces a large number of xylary elements having vessels with wider cavities. The wood formed during this season is called springwood or early wood. In winter, the cambium is less active and forms fewer xylary elements that have narrow vessels, and this wood is called autumn wood or latewood. In temperate regions, the climatic conditions are not uniform through the year so annual rings are seen in temperate zone trees because xylem cell varies with the season.

So, the correct answer is 'Xylem cell size varies with the season'.