Plastids

Plastids are organelles produced and protected by membranes inside plant cells that make food, store food, and provide plants with their colors. The specific type of plastid present in each plant structure decides whether that part looks green, shows other bright colors, or appears colorless.

The three types of plastids

• Chloroplasts contain a green pigment called chlorophyll, which gives leaves and stems their green color and produces food.
• Chromoplasts contain many different colored pigments, which give flowers and fruits their distinct colors.
• Leucoplasts contain a colorless pigment and are found in roots and seeds, where they store starch and protein.

How chloroplasts make food

Chloroplasts are the plastids responsible for making food for the plant. Plant cells need sunlight to make their food, and the chlorophyll pigment inside chloroplasts absorbs this sunlight. Without this pigment, the plant cannot absorb the sunlight it needs. In addition to capturing sunlight, chlorophyll is the pigment that gives leaves and stems their green color.

Structure of a chloroplast

A chloroplast has an outer cell membrane and an inner cell membrane, with an intermembrane space between the two. Together, these membranes form a protective layer known as the envelope. Inside the envelope is the matrix, which is similar to cytoplasm in a cell and contains DNA, ribosomes, and proteins. The chloroplast also contains structures stacked like coins called granum, where each individual coin is a thylakoid that holds chlorophyll.

Chromoplasts and leucoplasts

Plastids also decide the colors of other plant parts and store essential food supplies. Just as leaves contain chloroplasts and chlorophyll, flowers and fruits contain chromoplasts with different pigments that give them their varied colors. In contrast, leucoplasts have a colorless pigment, which is why plant roots and seeds look colorless. The main job of these leucoplasts is to store starch and protein securely inside the plant cells.