What conditions are necessary for the formation of starch in the leaf?

In order for starch to form in the plant leaf, the process of photosynthesis must occur. For this process to take place, sunlight, carbon dioxide in the air and water are needed. At first, sugars are formed, from which then starch. This is confirmed by experience: any plant in a pot is placed in a dark cabinet for 2 days, then taken out, part of the leaf is covered with dark paper and placed in bright light for 12 hours. Then the sheet is cut off, the paper is removed, put in boiling water and treated with hot alcohol. A discolored sheet is obtained. If you drip with iodine, then the area that was not covered with paper will turn blue. Conclusion: starch was formed in the leaf during photosynthesis.