Plant Kingdom Question 613
Assertion : Pinus does not show formation of annual rings. Reason : Pinus grows in area of environmental fluctuation.
Options:
A) If both the assertion and the reason are true and the reason is a correct explanation of the assertion
B) If both the assertion and reason are true but the reason is not a correct explanation of the assertion
C) If the assertion is true but the reason is false
D) If both the assertion and reason are false
Show Answer
Answer:
Correct Answer: A
Solution:
Secondary growth takes place in a manner similar to that of a dicotyledonous stem.
The secondary word shows well marked growth rings which are formed annually due to environmental fluctuations.
Each annual ring possesses a zone of spring and an autumn wood.
Spring wood is formed during the growing season under availability of enough water and minerals.
It possesses large polygonal, thin walled and wide tracheids with large bordered pits.
Autumn wood is formed during the autumn season.
It possesses smaller, squishy, thick walled and narrow tracheids with small bordered pits.
It is evident that the size of tracheids shows a marked variation with regard to the amount of water available in the respective season.
BETA
