How many types of plastids are there?

There are four types of plastids based on their stages of development and the presence or absence of biological pigments. 

Chloroplasts

Chloroplasts are green plastids found within the mesophyll of the plant cells. Chloroplasts contain chlorophyll pigments and serve as the site for photosynthesis in the cells. Chloroplasts may convert into chromoplasts. 

Chromoplasts

Chromoplasts are highly pigmented plastids usually found in flowering plants, fruits, and aging leaves. They contain carotenoid pigments, which give flowers and fruits different colors. The bright colors serve the purpose of attracting pollinators. 

Gerontoplasts

Gerontoplasts are essentially chloroplasts that are going through the aging process. These plastids occur in leaves that no longer carry out photosynthesis. When the leaves of a plant no longer use photosynthesis, such as during autumn, the chloroplasts develop into gerontoplasts. 

Leucoplasts

Leucoplasts are non-pigmented, colorless plastids usually found in a plant’s non-photosynthetic parts such as the roots. Their main function is storing proteins, starches, and lipids depending on the plant’s needs. They also play a role in conversion of amino acids to fatty acids. There are of three types of Leucoplasts:

1. Amyloplasts - store and synthesize starch
2. Proteinoplasts - store proteins that a plant requires 
3. Elaioplasts - store fats and oils that a plant requires