Plastids

Plastids – Colourful and Storage Organelles of Plant Cells

1. Structure and Similarity with Mitochondria
Plastids are double membrane-bound organelles found mainly in plant cells.
Just like mitochondria, plastids also contain:

• DNA

• RNA

• 70S ribosomes

These features allow plastids to synthesize some of their own proteins.
However, plastids are usually larger in size than mitochondria and can be seen easily under a light microscope.

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2. Classification of Plastids Based on Pigments
Plastids are classified into three main types, based on the type of pigments they contain:

1. Leucoplasts – Colourless plastids

2. Chromoplasts – Coloured plastids (other than green)

3. Chloroplasts – Green plastids involved in photosynthesis

This section focuses on leucoplasts.

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3. Leucoplasts – Nutrient Storage Units
Leucoplasts are colourless plastids as they do not contain any pigments.
They occur in various shapes and sizes, depending on their specific function.
Their main role is storage of nutrients, and they are further divided into types based on what they store:

• Amyloplasts: Store starch

• Elaioplasts: Store oils (lipids)

• Aleuroplasts: Store proteins

These plastids are commonly found in non-photosynthetic tissues like roots, tubers, and seeds where storage is essential.

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Conclusion
Plastids are vital organelles in plant cells, performing varied roles from photosynthesis to storage.
Leucoplasts, although colourless, are highly important for nutrient storage, ensuring that the plant has energy and building blocks available when needed.