Explanation
Guard cells have thick inner wall. But it is possible for guard cell to have chloroplast, since it is an epidermal cell? Very correct! But be mindful that guard cell is the only epidermal cell that has chloroplast. We already know that the guard cell controls the opening and closing of stomata - when the guard cell is turgid, the stoma opens, when it is flaccid, the stoma closes. It becomes turgid after it has absorbed water from the neighbouring cell. How is it osmotically superior to those cells? It is just because it has chloroplast and can produce sugar, which can afford its higher concentration when compared with other epidermal cells. Is it Ĩlear? Good!