What is the purpose of plastids in plant cells?

Plastids play a critical role in plant cells, primarily associated with the process of photosynthesis. They are membrane-bound organelles found in the cytoplasm of plant cells and are crucial for converting light energy into chemical energy through the synthesis of glucose. Specifically, chloroplasts, a type of plastid, contain chlorophyll, the pigment responsible for capturing light energy, enabling plants to produce their own food. This process not only supports the plant's growth and metabolism but also contributes to the oxygen supply in the atmosphere.

Other functions of plastids include the storage of starches or oils (in amyloplasts and elaioplasts, respectively) and involvement in the synthesis of various important biomolecules. However, the defining feature of plastids, particularly in the context of the question, is their integral function in photosynthesis, thereby making photosynthesis the primary purpose of plastids in plant cells.