Destartching is the process or removal or use of all the stored starch of the plant.
It is tby keeping it in a room for 2 or more days but be careful that the plant don't die
Plants get destartched when kept in dark for 2/3 days because in dark they are not able to prepare their food and store it so the use all their stored startch to perform the living functions hence destartching themselvesp