Concept:
Plastids are semi-autonomous double-membrane-bound organelles found in the cells of plants and algae. Based on the presence or absence of specific pigments and their metabolic role, plastids are divided into three major classes: leucoplasts (colorless storage plastids), chloroplasts (green photosynthetic plastids), and chromoplasts (colored, non-photosynthetic plastids).
Step 1: Understand the nature of Chromoplasts
Chromoplasts are responsible for synthesizing and accumulating fat-soluble carotenoid pigments, such as carotene and
xanthophyll. These pigments give parts of the plant—like flower petals, ripening fruits, and certain roots—their characteristic bright yellow, orange, or red colors. Thus, the plastid containing and storing xanthophyll is the chromoplast.
Step 2: Review and eliminate the alternative options
• Option (1) Amyloplast: This is a type of colorless leucoplast specialized specifically for the synthesis and storage of starch granules (e.g., in potato tubers).
• Option (2) Chloroplast: This contains chlorophyll and carotenoid pigments mainly dedicated to trapping solar energy for photosynthesis, giving plants their green appearance.
• Option (4) Aleuroplast: Also known as a proteinoplast, this is a specialized leucoplast that stores proteins (e.g., in maize grains).
This confirms option (3) is uniquely correct.
