Here's why:

* Photosynthesis: Chloroplasts are the sites of photosynthesis, the process by which plants convert light energy from the sun into chemical energy in the form of sugars (mainly glucose).

* Chlorophyll: Chloroplasts contain chlorophyll, the green pigment that absorbs sunlight and initiates the process of photosynthesis.

* Sugar Production: Through a series of complex reactions, the chloroplasts use the absorbed light energy to convert carbon dioxide and water into glucose (sugar) and oxygen.

So, while sugar is transported and utilized throughout the plant, its initial production takes place within the chloroplasts of plant cells.