why it is important to destarch a plant before performing an experiment? please help

A plant is destarched before performing any experiment in order to prevent photosynthesis. If starch is already present then it will create hindrance in determining the correct pathway of photosynthesis which results in the formation of food. Destarching is done by keeping the plant in absence of sunlight so that the stored starch is used up, or by depriving a plant from carbon dioxide.