Why the other part of leaf do not contain starch?

The other part of the leaf, typically the lower epidermis or underside, does not contain starch because it is not primarily involved in photosynthesis. Starch is produced during photosynthesis in chloroplasts, which are predominantly found in the upper mesophyll layer where light is absorbed. The lower part of the leaf has fewer chloroplasts and is more involved in gas exchange through stomata, rather than in starch storage.