Theory:

     All of a sudden, the farmer noticed a small fruit hanging from a branch. It was an apple and looked as delicious as the ones he ate as a boy. He plucked it and bit into the juicy fruit. The memories of the fun he had as a boy came rushing back. When his daughter saw the changed expression in her father’s face, she started pleading harder.
 
     The farmer put down his axe. He understood that the tree was home to many lovely animals and provided them with so many things. He wanted his little girl to have the childhood that he had. He threw away the axe and said to his daughter, “I promise that I will never cut this tree. You and your friends will have your tree and your playground.”
Explanation:
 
Suddenly the farmer saw a small fruit hanging from a branch. Yes, it was an apple, and it looked as delicious as the apples he had eaten during his childhood. He plucked it from the tree and tasted the juicy fruit. All his childhood memories came back to him quickly. His face expression changed. The daughter who was seeing all this, requested him again, with more force.
 
The farmer decided to let the tree remain - he put down his axe. He realized that the tree served as a home for many animals and birds; he realized that it provided space and shelter for them. He felt his daughter should also enjoy the childhood fun that he had enjoyed. He threw away the axe and promised his daughter that he would never cut the tree; he also said that his daughter and her friends will always have the tree as their playground, as they always played around the tree.
Reference:
State Council of Educational Research and Training (2019). Term-1 English Standard-6. The Apple Tree and the Farmer (pp. 125-129). Published by the Tamil Nadu Textbook and Educational Services Corporation.