Question

Why mitochondria and plastids called semi autonomous organalles?

Answer 1

The organelles which contain their own DNA and reproduce independently of the nucleus. They are said to be 'semi-autonomous organelles' Chloroplast and mitochondria are called semi-autonomous organelles because they have their own genetic material (DNA) and are capable of synthesizing proteins required for their functioning. 

Answer 2

because they have their own genetic material and are said to be 'semi-autonomous organelles' Chloroplast and mitochondria are called semi-autonomous organelles because they have their own genetic material (DNA) and are capable of synthesizing proteins required for their functioning.