plants use a substance called chlorophil to make food using the sunlight. without the chlorophil,the plants cant make food which is usually in the form of starch.when a variegated plant is left in the sunlight,it cant produce food because it has no chlorophil. thats why when the plant will be tested for starch at the end of the day,it will not have any. becase plant require chlorophil to make it. which a variegated plant doesnt have