Question

What is meant by destarching and why plant get the destarched in 48 hours of darkness

Answer 1

Plants as you know are autotrophs. They synthesise their own food materials - starch as a result of photosynthesis.

Destarching, as the name suggests refers to De-starching the plant. In simpler words when a plant is kept in a dark room for 48 hours it can no longer prepare its own food due to absence of sunlight. So in order to live it uses the food (energy or starch) that it prepared earlier.
Thus by the end of 48 hours there will be no more starch left for it. So such a plant is called a de-starched plant.
Just like our phone loses battery when there is no charge and switches off the plant too is ready to die. But when exposed to sunlight it can synthesise food and live again.

Destarching is usually done during experiments like testing for the presence of starch etc.

Hope this helps you.