What is the primary function of plastids in plant cells?

The primary function of plastids in plant cells is photosynthesis. Plastids are double-membraned organelles found in plants and algae, with chloroplasts being the most well-known type. Chloroplasts contain chlorophyll, the pigment responsible for capturing light energy. This light energy is then used to convert carbon dioxide and water into glucose and oxygen during the photosynthetic process.

While plastids also play roles in storage—such as storing starch, lipids, and proteins—photosynthesis is their defining and most crucial function, as it directly relates to the plant's ability to produce energy in the form of glucose. Other types of plastids, like amyloplasts and chromoplasts, specialize in storing starch and pigments, respectively. However, the fundamental role of chloroplasts in converting light energy into chemical energy through photosynthesis is essential for plant life and thus underpins the larger function of plastids in overall energy production in plants.