chromoplast

Chromoplasts are plastids specialized for the synthesis and storage of pigments, giving many plant tissues their characteristic colors. They predominantly accumulate carotenoids—such as beta-carotene, lycopene, and lutein—imparting yellow, orange, and red hues to flowers, fruits, and some roots. In chromoplasts, the photosynthetic machinery is largely absent or nonfunctional, and thylakoid membranes are reduced, sometimes with abundant lipid-rich plastoglobuli. This distinguishes them from chloroplasts, which are primarily photosynthetic.

Chromoplasts arise through differentiation of other plastid types. They can originate from proplastids in developing tissue or by transdifferentiation from chloroplasts or leucoplasts. In many ripening fruits, chloroplasts convert to chromoplasts as chlorophyll degrades and carotenoid biosynthesis begins, resulting in color change from green to yellow, orange, or red. Chromoplasts can also form in petals and roots where pigments accumulate.

Functions of chromoplasts include attraction of pollinators and seed dispersers, protection of stored lipids, and provision of carotenoid-derived metabolites such as signaling molecules. The carotenoids stored by chromoplasts are also nutritionally important for animals, contributing to human dietary vitamin A precursors and antioxidants. Chromoplasts thus play a key role in plant development and ecology, as well as in agricultural and nutritional contexts.