What role do chloroplasts play in plant cells?

Chloroplasts are essential organelles found in plant cells that serve the primary function of photosynthesis. This process involves converting light energy, usually from the sun, into chemical energy stored in glucose, a type of sugar. During photosynthesis, chloroplasts utilize carbon dioxide from the atmosphere and water absorbed by the plant roots to produce glucose and oxygen as a byproduct. This not only provides energy for the plant itself but also supports life on Earth by supplying oxygen and serving as the base of food webs.

The other options refer to different functions within plant cells. Storage of nutrients is typically the role of vacuoles. Water transport is managed by xylem and phloem tissues, which are part of the plant's vascular system, while seed development involves complex processes within specialized structures like ovaries, which transform into seeds after fertilization. Thus, the distinct role of chloroplasts in performing photosynthesis clearly identifies why this option is the correct answer.